It’s easy to choose your own user image or to set your normal background on your Mac, but what about if you want something else than the typical Aqua log on screen? Believe it or not, you can choose which background image appears during those few seconds when you log into your Mac. There are two ways to do this: you can use the excellent Visage Login, or, if you feel more adventurous, muck around in the Terminal window.
First, pick the image you want to use as background, set it to your exact screen resolution and save it to your user’s Public Folder. Then open up a terminal window and copy in the following text:
sudo default write /Library/Preferences/com.apple.loginwindow DesktopPicture “/Users/your_user/Public/myloginwindow.jpg”
Then, replace the your_user part with your own username, and myloginwindow.jpg with the full name of the image you want to set as background. Press return and enter your admin password. You’ll have to restart your Mac to see the changes and enjoy your new login window background.