Windows 7 Account Screen Editor (AES) is another tool that provides an easy way to customize the logon background.
Just download (777Kb) and run the program (right click and select ‘Run as administrator’). Click on "set background" and choose a picture for your logon screen. Or drag & drop an image inside the program. That’s all.
You can revert back to the system’s default background image by clicking on the ‘Default background’ button.
Moreover, if a picture is to large, ASE will automatically make the picture smaller. Download Windows 7 Account Screen Editor (AES)