I would run whatever pictures you have that meet your criteria with whomever is in it--scientists, nobody, JohnnyO at the beach in a thong, girls, pets, whatever. If they meet your rules, run whatever people vote on. They're the ones buying them.
I mean, I don't see the point of getting all worked up over gals wanting to pose with trucks. Most of the guys I know don't give a shit what they look like. Most of the gals I know take a lot better care of themselves and make an attempt to look nice in public. They want to show off a little. I wouldn't hang up a calender with stringy thongs on it because my wife would tear it down and throw it at my head. But if it were a mix and didn't have suggestive poses as you might find in the ones MAKG is refering to--those aren't gals posing, but being posed. It's a difference if you see what I'm saying. A mix that was truck focused I could hang up in the garage no problem. What jspafford posted is tasteful and my wife might say, "Who's that?" and I would say So and so's wife. If it were Ms December trying to wrap her legs around your head through the picture my wife would say "What's that!?"
That's my dollar twenty five's worth on the subject.