Do you mean a jukebox style machine? I'm currently building an easy to use "mp3 jukebox" for my grandmother since she has just moved into her new place. It uses Linux MCE and is a pretty basic smaller machine, with a touch-screen. Although it doesn't use iTunes, you can make a machine similar.
sorry for being unclear. I meant so that when your listening to a song, there's an app up, and it's the focus of the desktop. If you're just looking at the desktop, it's something about the song playing. Thanks
and theres a script for geektools iTunes info flying about somewhere on the geektools thread, that can show various info depending on how much ya fiddle an tweak, cant really think of much else,