How to Change the Logon Screen Background in Windows 7 through Group Policy
First, Create a jpg file you want as logon screen background which should be less than 256kb, name it as backgroundDefault.jpg and place it inside a server share, ex. \\servername\share\backgroundDefault.jpg Copy our wallpaper file to the user’s workstation. Instruct Windows to use our file instead of the default %WinDir%\System32\oobe\background.bmp file. With the Group Policy Preferences , we can copy our wallpaper to the user’s computer, while reserving the right to pull it off if the computer leaves the scope of the GPO. To copy files, open GPMC and follow these steps: