MY advice is to think about your character and what he is made of and why does he look the way he does. He must have a story, an origin. Think about his background. If he is some metal warrior guy, then maybe look at something like different medieval helmets and use designs you like to incorporate into your head. Also look at other tech or refer to other great artists who draw mech and space sci -fi stuff and get inspiration from that. When u have many inspiration and use a little bit for his skull, laser sight, mouth, skull and put into one concept and use your skill to unify the designs then u will have a master piece. When you are stuck on sculpting, look at other sources of inspiration.