Custom your toon. Something I have thought about for a while now.

Don't remember what pod cast # it was but you were talking about pimping your mount and toon. It's cool they added the barbershop but with gear on no one can really see what changes you have made. Pimping out your mount is a cool start.
I have always thought that crafter's (cloth, leather blacksmith) should be able to add custom colors when they make something..

IE Your a leather worker. Someone comes to you with the required mats to make an item. Well WoW should also have a extra ingredent to add a color. It would all be the same item but just have a different skin so you can dress your toon like you want. Or also have the option for higher blacksmiths to take something like shoulders/chest that drops from Naxx and put it in you trade window and change the color of it.

I think the game is only going to get bigger in the future. Think about it. Only 3 land masses in the "world"? The chances to fully customize your world is endless.