You like to over contrast and over sharpen things, that will not get you anywhere. Work to please the eye with natural light and not gimmicks.
I love the sig, but I think you've got the wrong render for the job. the render is giving off a comic book type feel while you're trying to give it a realistic 3d background. The two styles are clashing and you're render is sticking out far too much to make the sig overall enjoyable. I do love that background and the C4Ds in the front though.