Last.fm is an awesome app that lets you keep a record of all the music you listen to (which for me is mostly bands like Camera Obscura). Now you can use the artwork for your musical history for your wallpaper with John's Background Switcher integration. You can choose from the following:
- Recent tracks
- Top albums
- Top artists
Note that the size of song and album artwork last.fm stores is pretty small so it works best if you choose one of the montage modes for your background.