Though I really can't see where I would ever use 'Super Heroes' in a Star Wars setting, Super-Villains are another matter. There is a lot of inspiration to be found in the Marvel Universe—even if you 'change the names to protect the innocent', there are some great ideas here for use in Star Wars.
A group of 'super powered' (or in the case of this conversion, just very competent) beings dedicated to increasing their own wealth and power. They could exist during the Empire era as a criminal organization, operating against both the Empire AND the Rebellion. Post-Empire, they could be a group of terrorists operating under a leader bound and determined to rebuild the Empire in his own image.
The leader of the group, Zemo would be a skilled scientist/engineer as well as a clever politician and tactician. He would also be a highly trained and ruthless combatant. Though he may support Palapatine's rule through fear doctrine, his megalomania is such that he could never see serving another while he could be master. Thus, while he is 'evil', he is also seeking the downfall of the Emperor (to be replaced with himself, naturally). This could be interesting as he may occasionally act to help the Rebellion (when it suited him), providing the chance for a brief, but eventful 'alliance' (which is sure to fall through when he betrays the the Rebels as well). Zemo would be fabulously wealthy, able to support a number of secret bases as well as a small army of underlings to support his team.
A clever inventor who has perfected a suit of flying battle armor. Originally, he used this to pursue a life of crime, but was eventually taken in by Zemo (likely rescued from prison) and put to work serving this new cause. Though self-centered, he isn't moustache-twirling evil, and so may one day turn against his master, but for now, the idea of working with a 'team' (and having a plan) appeals to him.
A technological savant. He is capable of designing and building various high-tech gadgets, weapons and vehicles used by the group. He would likely have droid henchmen with him and would be a whiz at 'slicing' computers. Fixer (his code name) worked for a time with Imperial Intelligence, but they did not approve of his radical (selfish and dangerous) experiments and so he eventually left. He is 'in it' for personal power and the chance to pit his intellect and inventions against challenges. Though not 'evil', per-se, he is supremely self-centered and does not believe in 'causes'. He works for Zemo because Zemo funds his work. Pure and simple.
A hulking humanoid with little subtlety. He's not terribly bright and likes being told what to do. He is the team's muscle, pure and simple, able to take and dish out a lot of punishment. While he would be naturally strong, this could be augmented by armor and/or experimental drugs (designed by Fixer and Zemo). Like Mach-1, Goliath (his alias), is not necessarily evil at heart, but he doesn't trust himself enough to make his own decisions.
And intelligent and ambitious woman, Moonstone (an alias, based upon a charm she wears) was once part of the Imperial social elite—a scholar of psychology who did many studies on mind control and manipulation to aid the Empire's internal security (she may have even had a hand in writing the Tarkin Doctrine of Rule through Fear). Unfortunately, she discovered she had latent Force powers and was nearly 'taken in' by the ISB for 'study' (and/or conversion). She escaped and was taken in by Zemo and now serves as his lieutenant. Unknown to Zemo, however, she plots to eventually take over the team—to become Empress herself rather than serve another. Zemo would have trained her in combat and her growing force abilities make her even more deadly—combined with her knowledge of psychology, she is especially good at manipulating others.
A street urchin who fell in with the wrong crowd, Songbird (the alias she has chosen), is an avian humanoid who's songs are capable of hypnotizing many species. She is also a skilled thief. She was used by a criminal organization in their schemes until her boss (and lover) was killed. Zemo rescued her from prison and has since pampered and protected her—making her feel as though she has a home. Of course the Baron really has no attachment to the girl, but the charade has worked thus far in assuring her loyalty. Fixer has since managed to create a gadget that amplifies her vocals, allowing her to target powerful sonic blasts as well as amplify her hypnotic singing when necessary.
The organization of Hydra works best in a Star Wars setting AFTER the fall of the Empire. It is started by a radical believer in the New Order—one determined to bring about it's return through any means necessary. Terrorism is the key here, as well as various plots to perhaps even resurrect the Emperor himself. The organization gets its name from a mythical beast that grows two heads for every one cut off—thus the many small, fanatical cells seem to survive no matter what is thrown at them.
MAGNUS AND HIS ACOLYTES
A young and idealistic Jedi during the Clone Wars, Magnus' beliefs were warped by the fall of his order. He believed that radical, bloody vengeance was the only way to bring down the Emperor and the Sith. Though he has abandoned the ways of the Jedi, he sees the Sith as his enemies as well. His powers as a Jedi have grown and his tactics turn increasingly more brutal. He does not care who gets caught in the crossfire of his vendetta—and indeed, he blames galactic society as a whole for their allowing the Jedi order to be killed and persecuted. Though ruthless, the power of his personality has attracted a great many followers, most of whom are fanatically loyal to Magnus' cause. In his view, what he does is not Evil, but necessary—thus, he is a tragic figure who is gradually becoming what he abhors. Magnus' Acolytes are skilled, and many are Force Users he found while they were still young. He limits the amount of training each one receives to a few distinct areas—wary of them turning their powers against him if they were all 'fully trained'.
An agile, amphibious humanoid with a sychophantic personality. He is a skilled thief, spy and assassin. He is capable of great leaps and acrobatic feats, can cling to walls, can spit a blinding mucous and even lash people with a prehensile tongue. He is generally unpleasant, but loyal enough (though mostly out of fear).
Something of a Force Prodigy, Mastermind is a young man found by Magnus and raised with the sole purpose of being able to read and control other people's minds. Though initially blindly loyal to Magnus, Mastermind is starting to 'come into his own', and is developing a distinct superiority complex to everyone around him—he still follows Magnus, but only because the latter can resist his powers...for now.
A massive, blob-like alien with prodigious strength and little else going for him. He is very loyal as long as he is kept busy demolishing things.
A Clawdite Shapeshifter, Mystique is an incredibly talented and lethal spy and assassin. She is Magnus' sometimes lover and deeply dedicated to both him and the cause.
Another prodigy, Destiny is an alien child found and raised by Magnus with the sole purpose of being able to forsee the future. Unlike Mastermind, she is still very loyal to her master.
A telekinetic prodigy, capable of ripping or blasting things to pieces with sheer application of Force energy. He is an angry young man who has never known a home before the one offered by Magnus.
A pyrokinetic prodigy (a very rare force talent). Pyro is as hot-tempered and rash as his alias would suggest.
A recent addition to the team, brought in to enhance its raw fighting power. This near-human mercenary is as bloodthirsty as they come, reveling in ripping things apart with his claws and teeth. For a time, he had been employed with the Empire as an assassin, but he was too vicious even for them (too uncontrollable). Magnus realizes Sabretooth could be a liability, but for the moment, he is useful.
A cyborg equipped with massive power-armor (all of which was supplied by Magnus). He is a walking tank, providing pure muscle for the team, along with Sabretooth and Blob).
Victor Von Doom is the iron-fisted ruler of the remote world of Latveria. Though ostensibly bowing to the Emperor's will, he is a megalomaniac of the first order who would like nothing better than to rule the Galaxy, himself. He is a scientific and technological genius, but also a dabbler in the Dark Side of the Force. This, plus the resources of an entire planet behind him make him dangerous indeed. It is likely he would pursue the Rebellion in an attempt to make himself look good in the eyes of the Emperor. It is just as likely that he would use the Rebellion to help him eliminate rivals to his rise (rivals such as Darth Vader). Thus, players could find themselves working against the Doctor on one occasion and with him on another.
To the galaxy at large, this is merely an ancient society that has long served the indulged ruling class of the Republic (and now the Empire). But behind the scenes, a secret cabal of Force-Users and their henchmen have, for centuries, been attempting to manipulate the course of history and 'rule' from behind the scenes. They see the galaxy has a chess-board and its beings as pieces to be moved by them. Thus, the 'titles' in their order are all based upon this strategy game. To keep balance (of a sort) between the various huge egos involved, there are four co-rulers of the club:
Black King — Sebastian Shaw
A powerful, yet subtle manipulator. Shaw is outwardly a successful businessman. Among the order, though, he is the de facto leader, developing intricate plans to be carried out by the lesser orders (bishops, knights, etc.) of the club. Though putting on refined airs, Shaw revels in bloody, personal combat (and especially the application of his powers in it).
Black Queen — Selene
A sinister and beautiful woman, Selene has been a fixture in the order for many years—and yet she retains her youth. She does this via a specialized Force energy drain, becoming (in effect) a 'vampire' of life forces. Though vain and petulant, she is incredibly intelligent and manipulative—a perfect partner for Shaw (though a dangerous one, since she craves the 'life force' of Force users above all others).
White King — Donald Pierce
A rarity within the Club, Pierce is one of the few non-Force using members to have risen through the ranks. His technological genius and sheer ruthlessness earned him his spot. His cyborg body and combat skills have allowed him to maintain it. Even so, he is often looked down upon by others in the club. His partnership with his queen is one of convenience—each sees the other as a means to maintain power, and for the moment, that suits both.
White Queen — Emma Frost
As cold as she is beautiful, Emma Frost is a powerful Telepath who is fond of mind control and manipulation. She also possesses the rare Force ability of Cryokinesis. She is unabashedly power-hungry and selfish, willing to use or betray anyone in pursuit of her own goals. She and Selene are bitter rivals—a fact not helped at all by the torrid affairs Frost has indulged in with Shaw from time to time.