I'm a sucker (pun intended) for seeing the ladies' nipples.  While the rest might be really beautiful, the thing that gets my true attention is when there is no fear to show their nipples or at least one of them.

I prefer to see a nice smile in at least one of the pictures. Most men are very visual and a smile is always welcome

Small on top. No tats. No unusual piercings (ear and naval are fine). Pretty smile. No photo with butt pointing towards the camera so that it is all that is vislble. Isn't dressed like a gangster or wearing clothes with holes where holes shouldn't be. Perhaps in short - the girl next door.