I have two monitors, different sizes, and I'm using Ubuntu 18.04.1 and Unity 7.5.
I switched from GNOME 3, where the wallpapers were shown OK (correctly scaled on every monitor size).
Now, on Unity, my desktop is black as the background color is set on Appeaance Settings. No matter which wallpaper I select (I'm only using the default ones) on Settings, there is no change at all. I have logged out and shutted down just to see if this later corrects by itself (there might be a miracle, ;D ), but no luck.
Other options in Settings work fine, such as the Theme, Launcer Icon Size, and so on...
Just once, the default wallpaper (red beaver) appeared as wallpaper, but in incorrect size (small into the bigger monitor, and viceversa).
Is there some configuration option or file that controls this? Please, any advise? I am not looking for different wallpapers on different monitors/workspaces, just the same wallpaper on every monitor/workspace, as in default configuration (I presume).