OK the main thing that jumped out at me was the shadow direction, which didn't seem to match the lighting setup you have. Also the guy doesn't quite appear to be standing directly in front of the mech. In the image below, I've traced the shadow direction which seems to come from nowhere (pink dotted line).
Shadows on the ground plane
must radiate from a certain point on the ground plane
. This point is directly below the light source, and I call it the Shadow Root (SR). So if we put the Shadow root into your scene, the shadow should be like this, directly under the mech's head, between its feet:
As you can see, this magnifies the problem of the human figure's position somewhat. He doesn't appear to be standing directly in front of the mech, so a bit of shuffling is in order.
Here I've moved the human down and to the right a bit so he appears to be standing more directly in front of the mech and his new shadow works with your original planned composition. The lines of the mech's head even point more directly at the human now.
If you want to read more about the Shadow Root (properly called the Normal Point), you should check out my 3-part blog article on it
The Shadow Root: Part 1
, Part 2
, Part 3
Hope you find all this helpful