Prevent changing start menu background
Prevents users from changing the look of their start menu background, such as its color or accent.
By default, users can change the look of their start menu background, such as its color or accent.
If you enable this setting, the user will be assigned the default start menu background and colors and will not be allowed to change them.
If the "Force a specific background and accent color" policy is also set on a supported version of Windows, then those colors take precedence over this policy.
If the "Force a specific Start background" policy is also set on a supported version of Windows, then that background takes precedence over this policy.
At least Windows Server 2012, Windows 8 or Windows RT
Not Configured - No registry values are specified.
Disabled - Any values that would be created by the policy in the registry are deleted.
Enabled - Adding, modifying or delete values in the registry.
Prevent changing start menu background can be found in the Group Policy.
Please navigate to Computer Configuration - Policies - Administrative Templates - Control Panel - Personalization folder.