You could make metal plates like duck said, and maybe add a main
feature that represents as a symbol of your head design, like a vent or wire/cable design.
Plus, if you want, add signs of damage/aging like scratches or rust.
I make my robot heads starting from one 512x512 side only, then, when done,
I reshape it to 256x512 (kinda like
Pate5's all-round tex tut), then copy and paste to the
other side. Maybe that could be a little easier for you. Good luck with your head.