Great stuff! Lots of detail - you obviously spent a lot of time on this.
If you are looking for suggestions - read on - but if not … I think it’s a great image.
The first thing that pops out at me is that there isn’t a lot of value difference between the foreground and background. Your subject kind of gets lost in the high-frequency details and bright areas of the background - i.e. they’re fighting for attention. You might want to try a few things: 1) Reducing the saturation of the colors in the background - and shifting them to a cooler palette. 2) Adding more “atmospheric perspective” - i.e. fog, or 3) Pumping up the Depth Of Field to bring focus back to your subject.
Note that in the concept piece, there are “spots” of background brightness, but overall the value of the background is lower than the subject. For example, look at the round structure that “halos” the helmet: In the concept, the halo effect is fairly subtle - vs in the render where it’s much brighter (and it gave me the impression of a “force field” around the helmet at first glance).
Regardless of those minor suggestions, I still think it’s an awesome image