Solution for changing Big Sur login wallpaper to custom.

applewarm wrote:

1. Just sharing a solution I've found on Stack Exchange. Credit to whoever discovered it.

System Preferences > Users & Groups.

2. Open lock to make changes.

3. Right click on user in left column > Advanced Options.

4. Copy UUID value.

5. Go to /Library/Caches/Desktop Pictures.

6. If it doesn't exist create Desktop Pictures folder.

7. Inside Desktop Pictures create folder with UUID value as name.

8. Right click on folder > Get Info.

9. Open lock to make changes.

10. Grant permission to Read & Write to user, admin, everyone.

11. Make sure FileVault and Guest user are deactivated.

12. Change desktop wallpaper.

13. Restart computer.

Big Sur will now always create a lockscreen.png file in the UUID folder matching the current wallpaper.

Tested on a 2018 MBP and works perfectly.

Enjoy!

Can we see a screen shot of your modified folder as you indicate:

 /Library/Caches/Desktop Pictures

Here is what I see by default:

for clarity are you saying create another sub folder with a tile of the UUID?

Do you place another picture in that folder, do you name with UUID number or do you name it "lock screen.png" ?

Do you delete the old "lock screen.png" ?

Right now that "lock screen.png" matches my login background, not the colorful Big Sur restart wall paper...?