Desktop Background GPO setting not working as expected

Hi there,<o:p></o:p>

I'm using Windows Server 2008 R2 ADDS and my client machines are Windows 8 and Windows 7 Prof. I've configured a GPO to deploy an image (.jpg) as desktop background at the same I want user would be able to change the background if they want. Unfortunately it is not working as expected. User can see the wallpaper as background but unable to change it.<o:p></o:p>



From client desktop i can click on 'Desktop Background' and select other picture locations. Finally clicking on Save Setting does not have any effect. The background image is the same that I've deployed using group policy. 

Does anybody know how to resolve the problem?<o:p></o:p>

Thanks<o:p></o:p>

Enam<o:p></o:p>