Do you sketch out your drawings before going into them? It might help with the placement of the neck, shoulders, and arms if you do a basic anatomy sketch underneath everything. The neck comes out of the base of the skull and the lower jaw, but it looks here like it just comes right out of the back of her skull, and it flattens her. Reference photos will do good, I use them ALL the time. It's not cheating to reference stock photos! I like the colored lighting, but there are some inconsistencies. For instance, there is a highlight on the shaded side of her face that is behind her hair, but there is no blue highlight on her lips, which are not in shadow. Also, the lighting seems to be coming from slightly above, but the brim of her hat doesn't cast a shadow. Everything with mass will cast some kind of shadow, and shadows aren't always just blobs of darker shapes. If you look at people on sunny days, you'll see that things can sometimes make crisp, definite shadows.
Overall, this is very good, but just needs a little bit more work to push it further. Great job, fellow artist!