I read and see so many people trying to imitate a few of Audrey Hepburn's looks. All of the ones I can remember do not have the Winter coloring necessary for wearing black; read color experts, not everyone can wear black. Most do not have her body shape. Style icons look good oftentimes because at the very least, their clothes are tailored to them, but also because they have a signature style or wear their proper colors or styles.
I think it is a good idea to look for inspiration, but do not limit yourself to style icons, look in movies, blogs, history books. Look for inspiration (for your body type, coloring, and style type) not imitation (this is what bothers me about those who wear vintage without modernizing it; they look in costume). Style icons are famous for their unique looks.
I know I have mentioned this blog ad nauseam, but it really does have it all. Fit, body shape (more than the unrealistic four or so one usually sees listed) coloring, signature style, sheen versus texture, texture versus softness (for touch sensitive people), color contrast, value contrast, body proportions, capsule wardrobes, face shapes for hair styles and jewelry types, etc.