I'm a big Blender fan, and I've got general comments on all three of your "mech" models.
The design is nice, with proper attention to detail on the geometries. Kudos on beveling your edges, but everything is too low-poly. I can see those polygons in the feet, in the gun ... actually just about everywhere. You would be well-served to increase the detail of your mesh. I realize that this is not a simple fix, and that you'll have to go back and re-do most of it, but that's one of the biggest weaknesses.
Your lighting and materials aren't realistic. You should add more lights that are much dimmer (brightness 0.100-0.400), that don't cast shadows, and that don't cause specular reflections (there's a "No Specular" button if you select the lamp and then go to Shading [F5]). Place them so the back of the mech is better-lit. Regarding materials, you made a good call wanting to add some noise in your textures, but don't use the built-in texture "Noise". Use "Clouds" instead; it'll give you a softer noise that you can control better. And make the two colors more similar (like 0.500,0.500,0.500 for the main color and 0.400,0.400,0.400 for the cloud-texture color). This would make a big improvement in all your models. And is there some kind of blue light coming from the left? All the blue on the back wall and on the mech's front looks out of place.
Finally, you made a mistake with the reflections. The back wall and left wall have "Ray Mirror" turned on, but they aren't reflecting the mech. I have no idea why that is, but look for a setting like "Only reflect objects in the same layer" or try putting all the objects in one layer. And the reflective "head" in the center of the mech looks strange: you should play with the various mirror settings as well as specularity (color, brightness, softness) and transparency. I don't know if you were going for a mirror-effect, a glossy-effect, or a glass effect, but it doesn't really look like any of those.
Thank you very much for your insightful comments.
Truth be told, these models are actually intended to eventually render some 100*100 pixels with, but I'll definitely keep your comments in mind when I move up to making some cutscenes (totally a plan of mine at some point)
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