I get the background image from http://2.bp.blogspot.com/_VR6AkJGhEw4/SwOij4dp_dI/AAAAAAAAoeQ/bCQAiIzICrA/s1600/IMG_4910±+Version+2.jpg
Nice character model!
Are you sure waistline is right? It kind of looks like his shorts should fall off any second. Don’t you think he needs a belt or something like that?
Also, his left arm could definately use less reflection of the white light. All of that excessive discoloratoon caused by the white sun causes the arm to blend into the background and appear blurry.
Finally, it might just be me, but his left calf muscle looks a little bit oddly formed.
But either way, you did a great job blending the photo’s atmosphere and the CG world into one convincing environment!
Looks great, other than what Amprod said. I think most of the lighting HDRI needed to be brighter and a little less bloomed… If you are using a blur for the bloom, you may need to lower it by 2 notches and you got it made.