Want your desktop, GDM background & Plymouth boot image to match? Using gargantuo‘s Global Wallpaper script you can easily do so.
Download the script @ gnome-look.org
Extract the archive
Open a terminal and navigate to the extracted folder
Install the script by running ‘sudo ./install.sh’
Now run ‘/usr/local/bin/global_wallpaper.sh’ in a terminal session (minus the apostrophes)
You will be promted to select an image file (png files only)
Once chosen click okay and the script will set it as your desktop wallpaper, GDM wallpaper and plymouth background.