Evolvotron is a random image generator using algorithmetic mutations. It sometimes generates stunning pattens, textures and inspirational art. Above image generated using evolvotron in just couple of mutations. And its available as a wallpaper for download at Gnome-look. A tip for beginners is to start with a tile that has lot of variations.
Evolvotron is available in Ubuntu universal repository and use following command to install it.
sudo apt-get -y install evolvotron
Check out help menu to get info on keyboard shortcuts and command line options.