http://inspirated.com/2010/11/17/howto-use-animated-xscreensaver-matrix-backgrounds-with-xfce
/usr/libexec/xscreensaver/glmatrix -window-id $(xwininfo -name "Desktop" | grep 'Window id' | sed 's/.*\(0x[0-9a-z]*\).*/\1/g')
If you then enable compositing and transparent windows beautiful things happen :D