To implement the same wallpaper to all users computer using group Policy follow the steps.
- Create a share network folder on one of the servers.
- Create or edit existing group policy
- In group policy editor under -> User configuration ->administrative templates ->Desktop ->Active Desktop
- Enable Active desktop policy
- Enable Active Desktop Wallpaper and Type the path to the Wallpaper next to the Wallpaper Name:
- Give users Read and Write permission to the Shared folder where the Wallpaper located.