This tutorial will guide you through changing the OS X login screen from the “Leopard wallpaper” to any image of your choice.
The first step is to download and install Loginox. Loginox requires OS X 10.5 or later. The installation is very straight forward – just open the .dmg file and drag Loginox to your Applications folder. Launch it from there
You’ll be presented with a window that shows your current login wallpaper / image, and a blank window where you can drag your new login background.
The image you set as your new login background should be 2560px by 1600px. I used the Gimp for OS X to crop and scale my image.
Once your image is sized properly, drag it into the New Login image ‘blank’ window of Loginox. That window should fill with a thumbnail of your picture.
Click the Set new Login image button. You’ll be prompted to enter your password. Do so.
Now the Current Login image pane will display your new login background image.
The next time you log out or restart your Mac, the new login screen will be displayed. If you ever want to revert to the default login background, just launch Loginox again and click the Reset to default button.