Ralph The Magician wrote:
There are three distinct "login screens" in macOS now.
1) Initial login after a restart or shutdown (disk fully encrypted)
2) Login screen after an initial login has occurred
3) The lock screen
1) Cannot be changed easily. It's the preboot phase of a FileVault protected drive. Everything encrypted.
2) Can be changed (and no need to disable FileVault) -> see below how to.
3) Can be changed by the user : Systems Settings -> Wallpapers
To change 2) :
- Set you preferred background in Systems Settings -> Wallpapers
- then go to Systems Settings -> Lock Screen -> Show message when locked -> enable the option -> set a message (you can disable it after) -> it will update the default login screen wallpaper to include the message -> that's the trick
- Quit Systems Settings
- Logout -> the new wallpaper is used for the login
Note : if you want to have a different wallpaper for login screen and for session : after step 2, redo step 1, then Step 3 & 4
Hope it helps