Follow the procedure below to change the Windows 7 logon screen.

1. You will need a registry file which can be downloaded here: click Extract the file and then double click it to add it to your registry.

2. Browse to this location:

C:\Windows\System32\oobe (“C” is your Windows Seven Installation drive)

3. Create a new folder named Info. Then, create a new folder inside the Info folder and rename it as backgrounds.

4. Copy the image file to this folder and rename it as backgroundDefault. Note that the image must be in JPG format and the size should be less than 256 KB.

5. When you reboot your system you will see the change.

The following files (sorted by width-to-height ratio) are supported in C:\Windows\System32\oobe\Info\Backgrounds folder:

* backgroundDefault.jpg
* background768×1280.jpg (0.6)
* background900×1440.jpg (0.625)
* background960×1280.jpg (0.75)
* background1024×1280.jpg (0.8)
* background1280×1024.jpg (1.25)
* background1024×768.jpg (1.33-)
* background1280×960.jpg (1.33-)
* background1600×1200.jpg (1.33-)
* background1440×900.jpg (1.6)
* background1920×1200.jpg (1.6)
* background1280×768.jpg (1.66-)
* background1360×768.jpg (1.770833-)

In building a base image for Windows 7, I wanted to set a default user account picture for all user accounts (the company logo). There is a Group Policy setting which allows you to apply a default user logon picture in the Welcome Screen for all user accounts.
Note: As Home Editions of Windows do not include the Group Policy Editor, you need to configure this setting using a Registry-based Policy. This article does not address that issue.

1. Click Start, type gpedit.msc and press ENTER

2. Go to the following branch:

Computer Configuration | Administrative Templates | Control Panel | User Accounts
3. Double-click Apply the default user logon picture to all users

4. Set it to Enabled

5. Exit the Group Policy Editor.

This policy setting allows an administrator to standardize the logon pictures for all users on a system to the default user picture. One application for this policy setting is to standardize the logon pictures to a company logo. If this Policy is enabled, the Welcome Screen uses the default user picture which is stored at %PROGRAMDATA%\Microsoft\User Account Pictures\user.bmp. The default guest picture is stored at %PROGRAMDATA%\Microsoft\User Account Pictures\guest.bmp. If the default pictures do not exist, an empty frame is displayed. To display your preferred image or the company logo, replace the file user.bmp (128×128 px) in the following folder:

%PROGRAMDATA%\Microsoft\User Account Pictures
Also note that if you enable the above Policy, you’ll see an empty frame at the top of the Windows Vista Start menu where the user account picture normally displays. And the Change your picture option in the User Accounts applet will be removed.