The black (or near black) background may be throwing off your values. Folks here recommend something closer to a neutral value (gray 128) to start from.
Here's what the image looks like with a gray 128 background:
Here are my crits:
The head has a bit of an odd shape.
The character design is a bit unclear. This could be a guy in a motorcycle helmet or a space marine. Or a robot with a faceplate. Maybe some accessories or decoration to help suggest what this person does?
The colors are a bit dark and desaturated. Maybe make them lighter overall, reduce the contrast in lightness and increase the contrast in hues. Consider making some parts of the outfit (sleeves, or maybe shoulders) a different color altogether.
Maybe try a light source from one of the upper corners, or directly left/right. Assume a decent ambient light too so the character is still visible overall. This may leave a large area of flat color in some spots (like on the chest), but that's perfectly ok.
Tourist
FYI, the file you saved includes a gamma correction factor. This isn't constant across systems/monitors/software. I'm pretty sure the image I'm looking at is much darker than the image you're looking at.
