How do I change the login screen background in macOS Mojave? I just updated to macOS Mojave, and immediately noticed a couple of things:


My custom login screen wallpaper is gone.
When you click on a user's name in the login screen, it switches to their personal background (their usual wallpaper for the first space on the primary monitor).


I assumed it had just overwritten my cached image file. But when I went to replace it, nothing happened. It turns out that com.apple.desktop.admin.png is gone entirely!



Right after taking that screenshot, I decided to poke into Desktop Pictures and found my personal login screen background, which looks promising. It contains one other folder, which  probably  (edit: confirmed) contains the login screen background of my administrator account.
I've fixed it! You'll have to edit the dune HEIC picture though. If you're willing, follow these steps:

​1) Go To: /Library/Desktop Pictures/

2) Find the file called "Mojave.heic"

3) Save a copy as a backup somewhere else

4) Select the picture you want to have instead

5) Edit image values (DPI, size, etc.) to fit

6) Rename this edited picture as Mojave.heic