1) How about a Death costume: Black robe, shaded hood with a hidden face and then we get to choose an eye color which would be the only thing you could see from the face, and no shoes except maybe be able to float.
2) Angel: Huge (or small) white wings, a skirtish thing (what Angels wear), a halo above the head, and for the shirt a white chest armor with epic detail.
3) Star Wars characters like Darth Vader: You might need to get permission for that...
4) Cowboy: Brown/Black Cowboy hat, leather vest, leather boots, leather chaps, jeans..
5) Mario Characters: Again, permission might be required.
6) Marvel/Capcom/DC: Again permission, but something like Ironman, Batman, Joker, or Spider-Man.
Those are my ideas, they may not be good, but I like them.