Don't know how to do it? Its just drawing :O
Just look at this head and create you're own version of it.
The picture is just an example :P
But really, drawing a robot head is one of the easiest thing you can do.
And the style you used looks good, but don't use it for the whole head, thats what makes it look like a pillow. Use many styles on the same head, use some clever design and get some good ideas.