A user on the Green Button found this Russian website which has a comprehensive selection of Media Center screen shots in Windows 7. Some very interesting new features and settings. With the screen shot below it looks like Microsoft have resolved the issue of the media library being merged in Vista by now having respective media libraries. So hopefully that will mean no more music album covers appearing in your pictures library!
Other new feature is the ability to rate your music and photos in Media Center and to then create playlists and sideshows based on those rating. Take a look at the many screen shots to get an idea for yourself what's new!