When it comes to music, i feel that it needs to be something light, upbeat and non vocal or very light vocals.
Unfortunately, I currently cannot think of anything suitable either, but music would be great!
I do feel we should stay away from the theme song of the mmo's we discuss here due to the fact that people may feel it shows favoritism, but then again, i keep thinking the theme to Trickster or Grand Chase would fit nicely.
One other thing, instead of just a plain white background, maybe put something with some color in, like a map from a game or something. Or maybe even if behind each picture of a character, we show the main splash screen for that game.