i love the jukebox idea!
maybe you can make it look like the inside of some sort of machine.. with like some kind of journey through and a machine like name for each area..
you can allow everyone who signs on to have kind of like a guide (not a real one) in the form of a robot or something.. and give them a name.. and characteristics.. and make them the user's friend (which they could be able to customise)
you can make up a myth-type story for the page and have different characters, one for each genre of music with specific characteristics that suite this genre and such.. and give it a quest-like atmosphere.. and have updates for new imaginary events.. you can even make the member take part in the action..
you can make it into a highschool cafeteria with the different cliques and their type of music.. (maybe a bit too prejudiced?)