Changing Mate Desktop Environment Lock Screen Background - Wallpaper
Even after all this time Mate Desktop still fails to allow you to change the default lock screen background. Well, after some poking around I discovered (by discovered I mean I actually did some tracing through the system. I didn't google it then stand on the shoulders of others all the while telling the world how great I am for 'finding' this information!). So to the point.
To set a solid background colour (anythings better than that awful sea green and orange default):
Toward the bottom of that file you'll find 2 values:
change the <default>HEX COLOUR CODE</default> values to your desired choice. Re-log either by quitting X to command line then starting it again or rebooting (we have to stop and start the settings-daemon).
I've not yet sussed out how to change the image Mate uses nor will I ever, I just didn't like that default vertical-gradiant at all, it made me feel sea sick!!