First the new roster for Ultimate Marvel vs Capcom 3 was leaked, now today alternate costumes have been leaked for all characters as well through people buying the strategy guide for the game early.
The alternate costumes are not color schemes or palette swaps, they are future costumes planned to be DLC. If you have the DLC costumes from Marvel vs Capcom 3, they will get transferred to the new game, so don't worry about losing them; the same applies to Jill and Shuma.
Those are all the single pictures I can find, but holy crap the new costumes are amazing. Best ones in my opinion is Hawkeye's Ronin and Deadpool's Cable costumes, they look incredibly good. I'm sure everyone will agree with me as well, but Udon Taskmaster is another great costumes. Another favorite one of mine is Magneto's House of M getup. These costumes are pretty appealing for fans, and Capcom has even thrown a bone for Megaman fans by giving Zero and Frank West Megaman costumes.
Yo, real talk, if I were actually getting this game, which I'm only not because I don't care about enough of the new characters, classic Jean, John Talbain Ammy and Planet Hulk Hulk would be so sick I would pay for 3 separate costume packs if I had to. That shit is sick yo.