when you set up MB you specify various collections (movies, tv shows, kids stuff) and each creates an entry point.
the program Media Center Studio will allow you to organize and arrange these entry points (and change their icons) so that when you click on them it takes you right into that library. initially i followed Game Browser's suggestion and created one collection (Games). After clicking on it you saw a box cover for each system. I changed it and created a collection for each system so they would have their own entry points and i could launch each one from the main menu (and add those cool icons).
another example, for my "movies" collection I used Media Center Studio to remove the default movie library. I added my MB one in its place, and I changed the media browser collection icon to match the standard one. so if you looked at my movies strip you would think it was just the WMC default until you clicked on it.