If you have already started using Windows 7 its time you should be ready for all the tweaks and software to get all customization you had been looking for Windows 7. Here is the first one for you, Logon Changer or call it as Login Changer, the first screen you are greeted if you have turned on password for your account.
Windows 7 Logon Changer lets you change the screen background and design to one of your favorite ones. You can select any image which will be used as background for the logon screen.
You should have an image which is less than 256 KB. In case you have an image bigger than this size, you can use Smush IT to reduce image size. Remember this is possible without any resgitry hack or folder settings change. Download Tweaks.com Logon Changer Via Channel 10
Update : Download some cool images for logon background Here on this SkyDrive link