I have my Mac configured to require a password when it goes to sleep or when the screen saver comes on. When I wake it up I'm presented with a login box and the screen behind it is flat black. I would like to change or add a background to this unlock screen but I'm not sure if it's possible. I'm aware of how to customize the background of the OS X startup login screen.
There is no resource in
There is no mention of a wallpaper path in
Secrets.prefpane doesn't have a setting.
I conclude: It's very likely impossible.