For a beginner with robot heads, that seems like a great start. To start off, if I were you, I would work on some of the colours, shade them down a bit to create depth and detail. Next you should work on the eyes, as they look very flat. Add some lines to outline the eyes to bring them out, if that doesn't look good, try some different styles out and some different techniques of shading. Also, I like what you have done with the tubes and mask, I'm not entirely sure what you call it, but I like it. It looks pretty good, but as said before, more shading and outlines should be improved on.
Right now that is a pretty good head texture, to improve, I would recommend youtube or just google images for robots. Just to get the idea of what they look like of course. 7/10 here mate, you're on your way to an exceptional robot texture maker.