Not bad but a few things are bugging me about this image. I can't really tell if she's standing up or laying back. The whole mood of this piece makes me think she's suppose to standing. If she is standing, I dont know about you but I cant hold that pose for more than two seconds. Since her legs are spread apart she would fall over immediately.
But then I see her hand and it looks like she might be pressing against the floor. But if she is on the floor, she looks like she looking up rather the down at some standing over her, which suggest to me she's standing.
It not bad and like it but the pose is very ambiguious. I'd work on it a bit more if were you.