As far as character developement I think they're nicely put together. Your experimentation with costume is nice but I think if you're interested in honing in on character sketches you should develop a personal language that brings more individuality to the face.

Also, don't be afraid or ashamed of picking up a coupe of fashion magazines to get a better feeling for clothing textures and patterns as well as body poses and positioning.

I love fashion magazines; they're great resources for when you're looking to do human characterization.