How to Change the Login Screen Wallpaper in macOS Ventura and Earlier:

A User Tip Authored by TheLittles of the Apple Support Community:

How to Change the Login Screen Wallpaper in macOS Ventura and Earlier:

Note: This is Applies to macOS Ventura and Earlier.

If you want to change the Mac's login screen wallpaper, but not the wallpaper on the Desktop, perform this clever trick.

I. FIRST: Create the Background:

1. Open: an image you want to use as your new lock screen background
2. Click: [the file name] on top-left corner of image
3. Click: the “V” on the right-side of the file name
4. Type: lockscreen.png for “Name:”
5. Select: Desktop for “Where:”
6. Press: return key

Screenshot:

II. THEN: Open Desktop Pictures in Finder:

1. Click: the Desktop
2. Click: Go menu in the Dock
3. Click: Go to Folder…
4. Type: /Library/Caches/Desktop Pictures in “Go to Folder”
5. Press: return key

Screenshot:

III. FINALLY: Set lockscreen.png as the lockscreen wallpaper

1. Double-Click: each folder until lockscreen.png is found
2. Drag: lockscreen.png from the Desktop to Desktop Pictures folder
3. Click: Move button in the popup window (Screenshot A.)
4. Click: Replace button in the popup window (Screenshot B.)

(Screenshot A.)

(Screenshot B.)