Wavin peeps, ran into an issue of the mate DE wallpapers not working after an upgrade.
I tried some tips from the siduction irc, the mate wallpapers only work on the test user the irc support had me make and test.
hopefully someone can help get it fixed.
https://paste.ee/p/SsIuk
You can try this, perhaps your dconf is corrupt, log in/out
mv ~/.config/dconf/ ~/.config/dconf.bak
There is also dconf-tools, I think you can change the background manually there.