Logon Studio, created by the Stardock team lets you customize your Windows Vista (also available for Windows XP) logon screen. Choose from many styles that will make your computer stand out from the crowd.
Logon Studio is freeware, which can set any wallpaper as your logon screen. All you need to do is to download this utility and choose the wallpaper you want to use.
Download Logon Studio here.
Logon studio lets you create custom screens within the program. Once you apply the screen, Logon Studio locks your computer so you can test drive the screen to see if it works for you.