Cool piece. I like the contrast between the two ends of the bg. My one complaint would be that with the monochrome feel that dominates the sig, the render feels a tad over-saturated to me. But that's largely personal preference.
Hmmm. One thing you could try is to toss on a black/white adjustment layer, and mess with opacity/layer masking to get a little more attention towards the render. Green can be a tough color to work with, imo.
You do really interesting things with your bgs. I'm not sure that the efx on the render match the bg stylistically, but that's hyper-nit picky of me. Great work on the shoulder patches!
I like the double exposure effect, I might've liked a little more BG, but for the look you've got here, it's not necessary and it could've been tricky to get it to look as clean.