The knees are too high making the legs look like some kind of tentacles.
You also made up a shadow that shouldnt be showing where the leg joins the hip (at least shouldnt be like that). Since you are using a reference, you might aswell pay more attention to it.
The thong straps are too straight to look realistic, you have to have in mind they wrap the body, and they arent glued there as if it were paper (and the pseudo AA, as Gil said doesnt really work). The tights (the top of it) have wrong perspective.
But really, as said, if you are using a reference, you should pay attention to how shadows are placed and shapes and so on, even if you are under restrictions from the hi-res.
Oh and it's anatomical. :X