As we’ve mentioned before, there’s a hidden feature in Windows 7 that lets you customize your logon screen background to an image of your choosing. Power users probably had no difficulties following those instructions, but a free utility from Tweaks.com made the process even easier.
Now there’s another application that also lets you change your background, but with a slight difference. This new Login Screen Rotator lets you pick up to 10 logon screen backgrounds which it will then display randomly each time you login. All you have to do is browse for the files you want to use then click “Enable Settings and Exit.” If you ever want to revert back to the default screen, you can use the utility called "Remove files and settings.exe" which is included with the download.
Oh, and if you’re wondering where to get some good images for your logon background, don’t forget this resource.