A very wise friend once gave me this advice : the Best campaigns to produce for are : Normandy,Desert,Russia,and so on...
Ruskies and Finns might be good, I am also very much into the Desert campaign...but there people refuse to buy 8th Army for some reason...although I have so many sculpts done it's a sin no to put them into rubber...and then metal!!! D.A.K is also a clear shot!