Perhaps a project for someone who is good at this kind of thing - not me I'm afraid!
In XP I had a small utility which automatically changed wallpapers - you could specify things such as change wallpaper every day or every logon or every hour, and whether the wallpaper should be chosen at randon from a specified location or loop though all available wallpapers.
I have quite a collection of Dream files now - it would be nice to have a similar utility that works with them to keep the desktop fresh?
Cheers
Rowan