It has been said that when your character reaches a certain rank, it gets a new skin.
My guesses are:
Randall in ROR vest
Mike in MU Cap
Mr. Incredible with original blue suit
2nd dimension Phineas, Ferb, and Perry
Princess Vanellope
Syndrome as IncrediBoy
Sulley in OK vest
Santa Jack Skellington
Blue Mater from the first film
What do you think the character skins will be?