The ELITS desktop wallpaper that is present on the Windows Server 2012 images is set when the Windows image is built by ELITS and we do this by setting a local group policy in the image. If you want to be able to change the desktop wallpaper through the Control panel you will first need to change the GPO that have been set during the image build process.
- Logged in on your Windows server click Start and search for gpedit.msc, then hit Enter.
- Navigate to Administrative Templates > Desktop > Desktop, right-click Desktop Wallpaper and select edit.
- On the window that appears select the option Not Configured and then click OK.
Now you can exit the Local Group Policy Editor. The last step is to sign out and sign back in with your user account on the Windows server, after that the wallpaper can be changed like usual.