Not only changing your Windows 7 login screen is easy and save with the free tool The Thoosje Windows 7 login editor. It also comes with a library of free login screen backgrounds, Like great windows 3D logo's and various other Themes like Movie, Cars and many more.
You can change your Windows 7 Login screen in seconds savely and reverse settings it back to the previous and original login screen anytime. It's also comes with a browsing function to select your own images and has a build in control the image doesn't exceed the Windows 7 limit of 246KB for the maximum size of the Login screen image size. Of course it has a preview option so you can see the effect of the changes before committing to them.