I enjoy the colour scheme and the idea of this art. However it feels to me as if you gave the head texture a good go, but after that it appears you became disinterested in the shading and detailing for the body's textures.
What I love the most in art, especially so in metals/robotics are the shading and varying designs of the pieces. Take for example a sawed metal pipe; it has a dull shade/colour for its surface, but where the saw has cut cleanly through, the metal is all shiny and pretty.
Why I refer to a cut rod is to pertain to your texture set - it appears to be metallic, so why not add depth of colour and shading to give it a story and meaning.
Is the sun beating down on your poor robot? Well make the surface that is closer to the sun, brighter, and that which is further away, darker.
Did its owner start grinding and sanding it to make it all smooth and new looking? Perhaps he only managed to finish half the robot's joints? Why not make these textures different and tell the story of the forgetful owner?
The brightness of the metallic panel to either side of the visor is great! It shows really well that the two pieces are going off towards separate angles. With a light source, such as a car headlamp or a sun, you should really be able to take advantage of the shading and really make it much more meaningful.
Don't forget to show the WHOLE body some love, man!