All of the above.
Glamour/sophisticated, girl next door, nerd/geek chic, goth, pinup/rockabilly, lingerie - love them all. But her femininity must come through, even when she is dressed down.
My fave is a casual look - jeans & t-shirt, summer dress & sandals, shorts & tank top, etc. I also love seeing candid shots of the girls.
A few examples of jeans pics that I find casual sexy.