Quote Originally Posted by Dr Unne
I know it's possible because every time I reboot a computer at work, the background is reset. There's possibly a registry key that does it or something.
That's most likely achieved through a group policy rather than a command line script.

However, you can use the "reg" command to modify the registry from the command line I don't know how you can force the desktop to refresh from the command line though after you've updated the appropriate entry.