It took a while to gleen the WEB for information on how to do this. The attached instructions will guide you through the necessary steps to set and lockdown the Windows 7 PCs login screen to your desired look. Once implemented, no matter who logs in, no user "Personalize" changes will make your Company Log or Warning Message disappear.
How to Change Windows 7 Logon Screen Background
Figure 1 shows a normal Windows 7 login screen background. The Windows users can easily change the "User Icon" image via the user interface for changing the logon screen user icon. However, Windows 7 doesn't have a built-in Logon changer for customizing and changing logon background.
The Windows 7 logon background image is in the Windows System32\OOBE file folder
called background.bmp (1024 x 768 pixels in size). You cannot change the logon screen image by just renaming the default background wallpaper and copying a new background image into the oobe folder. If you try to rename the default login screen image background.bmp, you receive an error message (Figure 2).
The following instructions give you a work-around that will allow you to change the Windows 7 logon background.
The User Account Control (UAC) prompts for permission (Figure 4) to execute the Registry Editor program. Click on the "Yes" button to allow the Windows Registry tool to open.
If an OEMBackground DWORD entry already exists (Figure 5), set the value of OEMBackground to 1. If not, Right-Click on the "Background" folder and select new DWORD. Set the name to OEMBackground and its value to 1 as shown in the below screenshot. After changing the OEMBackground setting, you can close the Windows 7 registry tool.
Open the Windows 7 Local Group Policy Editor, by typing GRPEDIT.MSC in the search field and press enter. Edit the Windows Settings – Security Settings – Local Policies – Security Options – Interactive logon: Do not display last user name setting to Disabled (Figure 11).
After completing all above steps, you Logon graphic should hold to this new setting. Test your configuration by changing an Administrator's "Personalize" settings. Also create a user account and change the user's account "Personalize" settings.