The most prominent feature on Windows 8 is the new Start Screen. The Metro UI start screen is totally different from the traditional start menu in Windows 7 and previous versions of Windows. We have discussed in detail the features of the new start screen. The start screen allows users to change the background image from the list of available ones in Windows 8. In case you want to prevent users from changing the background image, you can set it from the group policy.
Open the Group policy Editor using the run command. Run-> gpedit.msc and press enter. Under the group policy, navigate to Computer Configuration-> Administrative Templates-> Control Panel-> Personalization.
On the right side, you can see the option “Prevent changing start menu background”. Double click on this setting and then select Enable from the options.
If you enable this setting, the user will not be able to change the look of their start menu background, and they will instead see the start menu background set prior to enabling this setting.
Click Apply and close the editor, now on users wont be able to change the background image in Windows 8 start screen.