Windows 2008 R2 group policy not applied to windows 8 Workstations, but applied to XP and Win 7

I have a Windows 2008 R2 Domain Controllers and have a Policy to put a specify wallpaper, eventuality i have to change the Wallpaper, this setting applied sucesfully in Windows xp and Windows 7 workstations, but not applied in Windows 8 workstations even if i run gpupdate /forcé,

Best Regards,

Thank you