Shoutbox

Sure there is, just write a script with a timer that randomly chooses an image from a predefined folder and set it as the current display picture.

Be warned tho, you can add display pictures but you cannot delete them. It won't make duplicate dp's tho, so when you added an image, and add the same one again it will just open the one already added to msn.

Took the liberty of making a simple version...

EDIT: Looks like that one in the database is more advanced than mine