mate lock screen background
God, I've spent ages googling this after I moved some wallpapers around and the lock screen background changed to a horrible gradiant. I should've looked more closely at the Arch wiki, of course, where I eventually discovered this entry . looking at /usr/share/glib-2.0/schemas/mate-background.gschema.override of course, I discover that I've already set this for an absolute path that's no longer valid. Sorted via the following amendement: org.mate.background] picture-filename='/usr/share/backgrounds/default.jpg' where default.jpg is a copy of my currently selected wallpaper. THEN you have to glib-compile-schemas /usr/share/glib-2.0/schemas/ and restart x