Not exactly a wallpaper, but a splash for GIMP. When one starts the GIMP application a splash screen appears. I never keep the default splash screen and here is the latest one I made.
When you start GIMP, you see the
splash-screen displaying short status messages while the program is loading all its components.
Of course, you can customize the splash-screen: Create a
splashes directory in your in your personal GIMP folder (/home/user_name/.gimp-2.x on Linux, C:\Documents and Settings\user_name\.gimp-2.x\ on Windows).
Copy your image(s) into this splashes directory. On start, GIMP will read this directory and choose one of the images at random.
Make sure that your images aren't too small.
I included the GIMP .xcf splash if one wants to modify it to their liking.