Hiya, I'm back! Thanks for letting me do a paint-over for your piece, it dusted off my painting skills a bit and learned some things, I hoep you will find this useful as well (
Okay okay, so there were a few things I tackled in the paint-over:
Anatomy
Reference = key to believable anatomy. If you don't know what for example hair looks like, you can try to figure it out yourself first, but our imagination can only stretch so far. That's where references come into play.
Real-life examples make the things you are creating more 'real', because it is based of something that exists in our world. The best references are the ones you can just put in front of you and turn, look and feel around. That's not always the case so Tumblr, Google and Pinterest are your best friends on that subject matter 
I adjusted the overall gesture a bit by adding tilts to her shoulders and hips . You can look up the term 'Contrapposto' for more examples of basic gesture dynamics (:
For her hair and face I looked up some refs from Pinterest & Google and I painted accordingly.
I noticed that the proportions were off, so what I did was selecting her head and copied and pasted it 8 times beneath each other. The average human is 7,5 heads (this is the standard scale I use for my characters, but you can experiment around).
So what I did afterwards was simply liquifying and stretching the body(parts) so it would match the copied heads. I suggest you studying Andrew Loomis' book about figure drawing if you want to learn more about that kind of stuff.
Design
Overall I really like your design, the shape language you used is really interesting. However, I saw you used very dark -almost black- values in some areas. Try to refrain from using those values/colors, because it tends to stick out and catch the viewer's eyes.
I toned those parts down with a grey tint and added some more highlights to define the materials. As for the materials look up references and base your design of real-live objects instead of things from your imagination. You will see that the design will look more believable and solidified.
I also adjusted the design to make the chest + face the focal point. I did that by toning down some elements at her boots since I thought it was a bit too much and then I framed her chest by adding darker values around it.
Overpainting
Whew, done.
So I hope I could help you out a bit with this overpainting and if you have any questions, feel free to shoot me a message 
