though today's Nintendo direct was rather average in my opinion, they announced that you'll be able to get costumes for Mario and Luigi in the Wii U version! that made me pretty excited for the game :P also, the PS3 version will have an Assassin's Creed 4 costume, and the 360 version will have one of Splinter Cell
here's some proof - http://www.nintendolife.com/news/2013/08/youll_be_able_to_dress_up_as_mario_and_luigi_in_rayman_legends
The Mario & Luigi costumes got my interest as well.
FYI: The wikipedia page of the game has listed 2 other bonus costumes. Pre-ordered copies of certain editions (probably all but Wii U) will have a bonus costume. WiiU owners who downloaded the challenge app (before May 2013?) will get a bonus costume in the full game.
I didn't receive any code for Assaassins Creed costume for Barbara, somebody has news about this? The code was some kind of exclusive for gamestop? I remember that I saw the preorder bonus in the description of the product on amazon.com