|Thanks, guys, I've found it. I figured there was some global option that I just couldn't find in the registry. I was going to resort to removing the option from each right click context menu from which it was possible. But I've found the global key that disables changing wallpaper in general. The thing is, it wasn't there to begin with!! If this key is NOT there, then you can change the wallpaper freely. But if it is there, then the only wallpaper that works is the image specified by the key. It's location is:|
with a REG_SZ key named Wallpaper, and it specifies the location of the wallpaper image via either the local path, or UNC.