Bring along three outfits that reflect your personal style. If you love dresses, bring em. If you never wear them, don't!
I wore Keds in my senior photos and I still look at them 7 years later and smile because I loved those shoes! Even if they weren't brand new.
I would recommend a nice mix- a summer dress, jeans and a nice top, and then one more outfit based on what you normally like to wear.