Pictures collage screensaver for GNOME
However, I've modified his screensaver so the collages can be limited to specific themes. Only ~10% of the mosaic-ed sub-images are now off topic, assuming you choose phrase-lists carefully. I also include a "wallsaver" script that sets keywords so the result goes to your background wallpaper desktop file. This gives you continuous dynamic desktop wallpaper of your favorite theme. Just type: wallsaver /var/local/themecollage/flowerwords # or whatever.