changing the background when start up login
How do I change the background during login. I want to change this background, and use my background that I made. ? I have MacBook Air
MacBook Air 13″, macOS 10.15
You may no longer do that. I suspect Apple considers the login background image part of the macOS brand, and they do not want users to change its appearance.
You may find suggestions, and they might even work for a while, but that change will not survive an incremental macOS update.