I use a Dell laptop with a docking station with 2 monitors and Loki. I don't have problem in changing the wallpaper when I use the laptop alone, without docking station and 2 monitors.
When I Use the 2 monitors the command
gsettings set org.gnome.desktop.background picture-uri file:///path/NewWallpaper.jpg
The funny thing is that suppose I have an "OldWallpaper" as wallpaper and I change it, via the previous command, to "NewWallpaper". If I ask for my actual wallpaper
gsettings get org.gnome.desktop.background picture-uri
the output is
but I still see the OldWallpaper on my desktop! The same happens if I manually click on the NewWallpaper.jpg and choose "Set as Desktop Background".
I've also tried with dconf Editor and, as before, there is no correspondence between what I see on my desktop (OldWallpaper) and the picture-uri value (NewWallpaper).
Also I've tried with
but the output is
set-wallpaper: command not found
Any idea about what is going on??