Arr I like this idea. Another pokemon mmo has done this idea well (PCO but now its offline hope I don't get in trouble for saying it). The pokemon game is no longer around but the idea was solid. What they did was sell pieces of clothing at many a pokemarts and also has some in the token stores. It varied from lots of customization options. It had shoes, pants, shirts, accessories (like sunglasses or eye patches), and hats/hair that would each be put on one at a time but also had full suit you could buy that would make the whole sprite change (IronMan, Wolverine, Spider-Man, and Batman as examples). This adds a lot to a game I believe since everyone won't have just the same two sprites anymore, and add just enough flare so people can have some personality. Another thing that could be done would be allowing fan to create the sprite work and submit them on the forums for approval (since sprite creation is rather simple for those who know what their doing) and that would ease some of the work staff would have to do.