Nice start. (disclaimer to everyone except AnnIshman: me and Ishman have chatted on IM about this)
If the light comes more or less from the right the top right of the dome-head should be light as well, the curve as is atm makes no sense.
Same goes for the lighting on the bottom and middle of face. It looks like a angled surface more than something that is curved.
Here is a cleanup/edit I made from an earlier version
- I first tried to get a clear base shape, without any lighting at all.
- Then I added some lighting, just the basics. Since you got C64 colours here dithering is more or less needed if you want a smoother gradient (which looks less metallic tho, on the other hand)
- I made the eyebrows a basically the same colour as the rest of the head, because i thought having dark ones made them look odd. They could be darker metal or rubber in yours, but I did not think it works. Also decided to not give any shading to the mouth thing in front, it could just be flat.
- I also edited your eyes, because I thought they looked odd how they were hudding the black corners of them. Also the shading on a lightsource did not make much sense. In the end I reintroduced the pupils, I think that works quite well.
- Dither and all that, not really much to say here, just dither inbetweens. Basically only used 25/50/75% dithers.
- I also added some AA, not a whole lot as the palette does not allow it.
I hope this helps.