Very weird. I have 16.04 and Mate installed on 4 machines and this just started happening on 1.
The Desktop icons cant’ be changed. If I go to Appearance and chance the icon theme, the mate-panel icons change, but not the icons on the Desktop or in Caja.
I’ve verified that all the ownership in my home directory (recursive) have been set to my user.
I even moved the “user” file from .config/dconf/user and let the system create a brand new one. Same problem.
dconf-editor shows the correct icon theme.
I’m at a loss . . .