OK, I'll give it a shot (no pun intended).....
Right, you have the rifle fitted out with bipod and telescopic sights. Typical sniper set-up...
How about positioning it at an open window. Use natural lighting. If you have a few dummy rounds (brass ones), having a few lying around helps. Place 1 or 2 B&W photos of an individual on the floor.....
I don't have any problem with the flash in this picture. However, I am also of the opinion that a camo backdrop would have improved the mood of the picture, plus, it's OK to have crumpled camo.
My 2 cents.
Bernard