Setting dynamic desktop images on Linux
UNIX/X users: download the script called xplanet-display-root and run that from cron as per the instructions in the top of the file. Note that for the script to have permissions to access your X display, you'll need to run this shell command each time you log in to X:
bash -c set > $HOME/.exports
That outputs your environment variables in sh-compatible syntax, so the script can use them.