Nice job Marimo, I do see a few things that don't help this tag reach its full potential though. The first thing would be the flow of the c4d's, they don't really match the flow of the render so it gives off that messy kind of feel to it.
The next thing would be the lighting, whilst green does fit with the render it looks unrealistic if you get what I mean. Some green lighting on the render would help reduce that look and would also help with blending.
You could also make the render really standout some more with some dodge/burn. Mainly in the areas where the green lighting in the background is, so that the render matches the intensity of the lighting.
With the c4d's that you have placed in front of him they don't really fit in those spots. Something seems off about them there, it does help with adding depth but you could make it even better. Try not placing the left one over his arm, instead try lowering it and go from the lower left corner and across his belly(not too much over his belly though.)Then filter>blur>blur more, the one on the right is fine but blur that one as well to match the one on the left.
The last thing would be adjustment layers, I'm guessing you have used some but try adding a few more. Play with an exposure and a curves A/L and a few more gradient maps just to help with the overall finish of the tag.
I hope that helps you somewhat as I know awkward c4d's are, especially when making the background out of them. If you want me to clarify anything I said I will be happy to do so, top effort though