They think very hard of characters they can create and develop the costumes to the character. Finding that right character can make them into a success as a hero or villain. There must be some very creative people in their industry.
That's one thing I have always wondered about wrestlers of all sorts: do they decide to be 'good guy' or 'bad guy' or is it imposed on them by their managers? I suppose a lot of it depends on who has the best physique and who the current stars are -- if there are too many pretty boys, you automatically have to be a bad boy, probably. For some reason, I have never seen a single wrestling match opposing two good guys or two bad guys -- that would make it more interesting because you would not be able to guess in advance who was going to win.