I used a post at Lifehacker to create my own, auto-updating, sunlight tracking wallpaper.
It is quite easy. It assumes that your Pictures directory is located at ~/Pictures. Change it in the script if yours is different. Just put it anywhere and execute it. If it doesn’t execute, just chmod +x changer.
Here is the script:
if [ !-e world_sunlight_map_rectangular.jpg ]; then
wget http://www.opentopia.com/images/cams/world_sunlight_map_rectangular.jpg && rm world_sunlight_map_rectangular.jpg && mv world_sunlight_map_rectangular.jpg.1 world_sunlight_map_rectangular.jpg && echo "Finished."
Save it in your home directory.
Use the normal wallpaper selector to set ~/Pictures/world_sunlight_map_rectangular.jpg to your wallpaper. It’s a pretty big image, so most screens will look fine with it. If you want to do anything else to it, I suggest you look into imagemagick or phatch. Note you will need to put the image manipulation in the script so it is run on the image every time you download it.
Then, install gnome-schedule from the repositories. It will add System > Preferences > Scheduled Tasks, where you need to add a new, recurrent task that runs changer every hour. After that, it should auto-update itself with no help from you.
It really is a nice effect. Since Gnome-Schedule uses cron, the linux job scheduler, doing this will add no background processes to your computer, or even slow it down in any way.
Most systems can get some sort of program that does this. Now we have one, and all it needs is one file!
I intend to create a script that does the installation at some point in time. I might even package it in a .deb!