Specify the 'Force a specific Start background' (Min:0 Max:20) Forces the Start screen to use one of the available backgrounds, 1 through 20, and prevents the user from changing it. If this setting is set to zero or not configured, then Start uses the default background, and users can change it. If this setting is set to a nonzero value, then Start uses the specified background, and users cannot change it. If the specified background is not supported, the default background is used. Counter Measure: Enable this policy setting to prevent users from changing the Start background. Potential Impact: Users cannot change Start background.

[max background id]

(1) GPO: Computer ConfigurationAdministrative TemplatesControl PanelPersonalizationForce a specific Start background (2) REG: HKEY_LOCAL_MACHINESoftwarePoliciesMicrosoftWindowsPersonalizationForceStartBackground