FM / schemas

/usr/share/glib-2.0/schemas

Name	Size	Mode	Actions
10_org.gnome.desktop.background.default.gschema.override	115	0644	edit dl rm
10_org.gnome.desktop.screensaver.default.gschema.override	125	0644	edit dl rm

Edit: /usr/share/glib-2.0/schemas/10_org.gnome.desktop.background.default.gschema.override (115B)

[org.gnome.desktop.background] picture-uri='file:///usr/share/backgrounds/Alma-dark.xml' picture-options='scaled'