First, edit the canvas size so that there isn't so much empty space on the top. It makes it look weird in your sig.
As for the actual sig, I really like it. The only thing is that the c4ds that overlap his back look a little weird, try erasing a few of them. Also, this was probably part of the render, but if you added that ball of light in his visor, I think you should take it out. The background looks really good.
4/5