Windows 7 Logon Background Changer is a free open source software that let you change the wallpaper of the Windows 7 logon screen (also known as "welcome screen", "login screen" or LogonUI).
|Windows 7 Logon Screen Changer|
It has been tested successfully with the final version of Windows 7 (RTM) and Windows 7 RC 7100. It works with Windows 7 Home Basic, Home Premium, Professional, Ultimate and Enterprise, in x86 or x64 (32 or 64 bits). It does NOT work with Windows 7 Starter (edition sold with most netbooks). It works also on Windows Server 2008 R2 (but you are not supposed to customize a server).
On a side note, this small program is WPF based, it's a nice technical demo of Windows Presentation Foundation capabilities for those interested in WPF. It requires a decent GPU for the 3D animations to run smoothly. It runs fine with my Radeon HD 3200 on my laptop computer, but it should also work with lower end graphic cards, albeit slowly.