Re: how do you choose your union room appearance????
I know this is a completely different game, but if anyone else views this question looking for an answer for the newest Pokemon (Black and White), it's here.
I don't know which game you're referring to, but if it's Ruby, Sapphire, Emerald, Leaf-green, Fire-red, or anything older, there's no possible way to do this that i know of (Except i DID here something about going to Hoenn)???. I think the option of changer your trainer type wasnt introduced until Soulsilver and Heartgold. The only known way to change your character in Heartgold and Soulsilver is by starting a new game and waiting for your type you want, or going to a Pokemon Center and asking a person on the left side in the Poke'Center in Violet City.
For Pokemon Black/White, open up your trainer card to view your badges and click the small icon at the bottom, left corner of the screen. It looks like a letter with a stamp. Directly underneath your character's name, tells you what trainer you are. Prescooler, lass, ace trainer... and so on. Tap your trainer type and it should change. There aren't very many choices, but I know for a fact, most or all of them look different from the other games. You may even say they look better. I'm sure there's some way, throughout gameplay, ...some way you can obtain more options for trainers to choose from. I'm sorry, i don't know how to get more choices.