Yeah, I agree that it could be more dynamic in general, a slightly lower camera with a sharper camera angle and less sterile lines from the walls would help it out methinks. I think the background looks too small for the character.

I think the background is diverting a lot of attention. Clearly the character is the most important part, and a background that hasn't been created using the same care will only detriment the piece. I think you can mess around with the lighting and camera angle to make the background less distracting and the ninja's form more exaggerated.
(oh yeah, and I like him with the mask on a bit more, to be honest. at least not completely off as it is now)
Good luck, man. You've done a fantastic job so far