Come on, Pat, what are you doing?
... You've 'Enabled', nView Desktop Manager, and clicked on 'Desktops', then, 'Properties...' - Good so far! ... You've clicked on the '2' on the right-hand monitor. Now you need to click on 'Change Background' and choose a different picture! - Then click on 'Apply' then 'OK' three times, ...... then, BINGO!, you should have different wallpapers!
ps, - It isn't rocket science! 
..... If I can do it, - anyone can! 