On the anatomy side, she would be more cute with a longer forehead, and the shape of her head looks a bit odd.
Wrong shading on her left arm, should be more in the shade towards the bottom.
The breast have a very good shape (nice feeling of weight), and the overall curves are well defined.
A stronger, second cold color would make the piece pop a lot better. For example the black blue light could enhance her forms even more.
That's what banding is, all those places appear as larger rectangles. Some of it is bad (wings), some not so much. Easy to fix though. It can cover several pixel ranks, even cross flat zones. When you get the eye for it and start looking, it's in every piece of pixel-art!
More about banding here.
Banding is when pixels line up, or end at the same x/y coordinates of the subgrid. In that case this grid becomes more visible or forming shapes / clusters which make the resolution appear less fine.
There are some tutorials for that on the web, if you specifically search for banding etc. Manupix also already posted you a link =) (this one actually informs about all the important things to know, like AA, Jaggies, Dithertechniques and more)
I like that you went down in colors now, seems the little perfectionist came through ^.^
To quote Super17: i also think your pieces could gain a lot from AA towards your black lines, and as transition inside the images lines / colorfields =)
Where is banding in this piece? I've never heard of banding before so I don't really know how to detect it.
Much improvement! Once you kill the banding and gain better colour control (something I still need a lot of work on) you should start seeing even greater improvement in your work.
Looks quite nice. Since you already know how to draw and paint you'll be set in no time.
I was kind of a hypocrite for mentioning the high color count before since my first or second submission was an endless array of colors. I was just aware of the mindset here.
I also used to band pixels (need to clean up some of my old portraits).
Looks much better then your other works. 
But still some ugly bendings here, especially at the left side of the chin and the hand. And the black lines would look better with some AA, e.g. the eyebrows.
Great!