You can easily change the login screen wallpaper in OS X El Capitan to any image of your choice. This will impact the appearance of the login window when you boot a Mac, and also when you are using fast user switching to change user accounts. The wallpaper image that is replaced is what sits behind those login locked screens, which by default is a blurry version of the active desktop picture wallpaper. The replaced customized wallpaper will be your picture without any blurred effects.
For those who have customized the login screen in OS X Yosemite, you’ll find the task is similar, whereas performing the same action in OS X Mavericks is quite a bit different.
This modified a system file, meaning you should backup OS X before beginning just to be safe.
How to Change the Login Screen Wallpaper Image in OS X El Capitan
First, ready the new wallpaper image file: Locate a large resolution picture of the image you wish to set as the new login screen wallpaper, be sure it matches your screen resolution for best results (it will resize to fit either way).
- Open the intended image into Preview app and re-save it as a PNG file by going to File > Save As > and choosing PNG as the file type
- Name the file “com.apple.desktop.admin.png” and put it on the desktop for easy access
For the example here, I picked a screen capture of Manhattan as taken from the really nice Apple TV screen savers for Mac.
Next, replace the login screen image with your customized version via Finder of OS X:
- Hit Command+Shift+G to bring up Go To Folder and enter the following path:
- Locate the file in this folder called “com.apple.desktop.admin.png” and rename it to “com.apple.desktop.admin-backup.png” or something similar so that you can restore to the default if you wish
- Now drag and drop the “com.apple.desktop.admin.png” file you saved in the first sequence into this folder
You can verify and see the change by bringing up the Fast User Switching screen, accessing the lock screen, rebooting, or logging out of the Mac.