((MODS: Please forgive this necro. Took me hours to find this information and this thread seemed the best place to put it.))
Below is a list of Costumes Trent can use taken from costumes.ini in DATA/CHARACTERS. I am not entirely sure every one of them works... but the ones I've tried do.
USAGE: Hit enter in single player, in the console window type "costume <costumename>" Example "costume orillion" or "costume tobias" or "costume ozu" (WITHOUT the quotes). Hit F1, Save your game, Load your game. That's it!