If you are bored with the default logon screen of Windows 7, you can change the logon wallpaper using LogonChanger

1- Click here to download

2- Launch LogonChanger, and click on Change Logon Screen, and select the image you want as Logon Screen.

And thats it, tweakslogon will change the Logon Screen for you. You even can test your new logon screen by clicking on Test. If at any time you dont want to use custon logon screen, you always can revert to Default logon screen.

Enjoy.