You've got a lot of good stuff going on here, the description of forms is good and the overall look of the piece. You've got a few issues though.
First is the anatomy. Most of the upper body looks good, although his left hand seems to have been put on backwards. We should be able to see his thumb there. The shoulder seems to come out and up, which seems wrong. Moving down, there's a problem where the thigh meets the hip. It seems weak there, probably to do with the size difference between the thigh and the rest of the body. It seems a bit too big and too round. The other thigh seems to be missing entirely, we should be able to see at least part of the curve. His right ankle seems swollen, and you might think about toning down the tension on the calves. They seem to be bulging as if he's flexing them hard, but the rest of the post suggests he's relaxed.
The figure overall looks too soft, especially compared to the sharply defined stone and the photo background. What you should do here is use harder edged brushes and define the shapes more, and blur out the background a little. Right now the stone and stars are stealing attention away from your main focus, the figure.
Composition is good. No complaints.
I don't really get where the streamers of light are coming from. They seem to burst forth from a random spot in his hair.
I think you're also cropping a bit too close at the top. It's creating a tangent with the edge of the frame.
Overall, as I said there's a lot of good here, but I don't know that I'd consider it a finished piece at this point. There's a lot of potential for you to push it further.