Color choices are good. It's muted and moody and fits the character in this pose. Since your intent was to experiment with light and depth let's look at that. There is a strong sense of light and makes it seem as if he's about to interrogate someone.
Depth is not very convincing. The beak looks as if it's going straight down and not coming forward. The shadow below the beak doesn't help. A beak coming forward would not cast such a long shadow, only something close to the face would of so. Or the main light would shave to be in front of him.
The eye lights look like they are on the mask. There needs to be a lighter shade to indicate a turn in the eye openings to suggest some depth in the mask to suggest the eyes are inside. It's too subtle right now.
The chest plate is farther from the light so it's wouldn't have the same intense highlight as the top of the helmet.