Click on the selection "Pager settings"
When the window labeled "Pager Settings" appears, select "Virtual Desktops" on the left side.
On the right side select the box labeled "Different widgets for each desktop".
Click "Apply" at the bottom of the screen.
Now you will be able to set the backgrounds separately
After doing the above, each desktop presented a dark screen with no icons
and the layout settings was set to Desktop.
On each Virtual Desktop (VD) I then set the background:
right click on desktop and select Desktop Settngs > View
but the common icons I had on the desktops before were gone.
So on each VD I changed the layout setting back to Folder View
and the icons came back (though I had to rearrange them to prior positions).
right click on desktop and select Desktop Settngs > View > Layout
and select Folder View
Now I have 2 VDs with different background with the same desktop icons