Changing the picture displayed when you log into your system is not an option Windows OS is ready for, but Logon Screen has been created for exactly this purpose. Logon Screen is one way to easily modify the background of the logon screen.
With InstantLogonChanger always have your Windows 7 logon background the same as your Desktop wallpaper or set it to any other image or color without any security prompts or changing system files.
Netwrix Logon Reporter is a freeware product for logon event archiving and reporting. The product consolidates the logon events from all Active Directory domain controllers and archives them. The commercial version provides reporting capabilities.