With Logon Editor for Windows 7 you can able to change background image appears on logon screen in Windows 7 and you can also set button transparency and the text shadow.
Advanced Logon editor allows to save preview of logon with user’s desired picture, name .You can save the current logon before making any changes to revert back to old logon you can use “Restore logon” option to restore earlier logon preferences.
After making changes to apply them click “Apply Logon”.
Logon Editor is freeware and still in beta.