Hello @JB306yxe
- Run gpresult /h report.html on the clients to check whether the GPO has been applied successfully
- Please also check the following registry key
HKEY_CURRENT_USER\Control Panel\Desktop\WallPaper REG_SZ empty value
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Wallpapers\BackgroundType REG_DWORD 0x1 (1)
Reference thread: set-accent-color-and-change-background-from-wallpaper-to-color-via-gpp-registry - You might just use Group policy to manage wallpaper: windows-server-2016-changing-the-desktop-background-using-group-policy
Hope this helps!
Best regards
Karlie