We have already seen Windows 7 Logon Screen Background image Changer which allowed to customize and set logon background image but you can select only one. I have found interesting tool which can rotate or automatically change Windows 7 logon screen.
Similar to what you do with Desktop Wallpapers in a Windows 7 theme, you can choose number of images, select a folder containing images to be set, Change the time or certain period after which Logon screen will change. This is something awesome because you need to do settings once and only once and changing of logon screen will be automated.
logon screen rotator
The program weighs 370KB [LogonScreenRotator.exe] and its portable, no need to install anything. Works only with Windows 7 versions so, if you have it then Download to give a beautiful touch to your system.