After a fair amount of reading forums and checking Bodhi Linux, Unity Linux, PCLOS/Enlightenment, etc., I tried the following:
Settings/Settings Panel/Screen/Screen Lock/Wallpaper, I click on Custom.
Next, I go to Look/Theme/Advanced, clear the check marks on the left, and
Assign the Calm-3 background. I click on apply, the whole display recycles,
and ... nothing changes. And when I go back to Screen Lock/Wallpaper, the
system has reset itself from Custom to Theme Wallpaper.
What am I missing here? The Wallpaper switcher works, but I can't access the
wallpaper from the theme itself. I'm happy to do it via CLI if that works.
Thanks once more for your patience, kind support, and hours spent putting
together this wonderful distro.