Changing background images


I want to change three standard backgrounds to a custom one:
[]Desktop background
]Lock screen background
[*]Login screen background

Right clicking desktop brings up a menu for selecting Desktop background, and that works.

But how do I change the other two? Is there a working menu for selecting those, or do I have to manually create a “theme”?


Lock screen background: System Settings - Display - Screen Locking - Wallpaper
Login screen background: System Settings - Startup & Shutdown - Login Screen (SDDM) - there is a button on the right side called Background