This question already has an answer here:
I'm writing an installer and need to change the All Users' wallpaper. I can do this from the group policy editor GUI, but need to do so from my installer. I can't just edit the registry as it gets reset by a GPO on login.
How do I apply the relevant administrative template via programatically (preferably
cmd.exe or via the registry)?
(for interest, it's
User Configuration > Administrative Templates > Desktop > Desktop > Desktop Wallpaper [sic]