So one of the things that pisses you off if your an admin is people changing the desktop image on computers even though you have set all the options to stop it. Well it turns out that even if you disable access to the settings you can still use a browser to change the image.
The best solution for this is to go into a group policy “User Config\Administrative Templates\Desktop\Active Desktop\Active Desktop Wallpaper” and set it to a non-valid image file. (Something none existent another words)
This should be all that needs to be done, even if the user changes the image next time they logon it’s goon again.