Watch my video on how you can easily change your background for Windows 7 log on form by just using your registry editor and changing OEMBackground to 1 and pasting my jpeg file in a directory within System32.
You no longer have to stare at the boring blue background in 7 again.
If you are using dial-up or do not have flash player then visit my regular text tutorial on changing the background on the Logon form in Windows 7 : http://johnsonyip.com/wordpress/2010/01/12/change-windows-7-default-logon-welcome-center-background-to-something-more-fun/