September 26, 2010 9:45pm Your smile is very natural without overworking your mouth so thats a very good thing. To improve on your photo I would suggest to get to know your body how it feels when posing. To turn this photo from a prom looking photo into a model session, it would have been helpful to have tilted your head and turn your face three quarters.
your shoulders are good but bring down y our right arm and let it hang in front of you.
and stick your hip out a little more
as for facial expression smile, then try a relaxed look with your lips parted just a little. try redoing this photo and exploring different ways to model the dress