minor quirk to point out if I may...the planes on the head seem slightly off from each other, for example the chin is on a slight incline (estimated guess @ 15-25degrees) but the nostrils are on a larger angle (closer to 40-45degrees) & the horizontal forehead seam seems to be at a different angle from those 2 ( roughly halfway between the previous 2 @ approximately 25-35degrees). just nitpicking for the sake of bringing it to your attention in case you hadn't noticed it so you can correct yourself easier than much later on. my wife points out the oddball angles on my drawings that I don't notice & I find it extremely helpful in making sure I'm checking angles so that everything lines up appropriately. like I said though excellent work & I only really noticed those angles cause I've trained myself to do that for my drawings. definitely getting a from me regardless & can't wait to see the finished product.
here you go... here's a link to it I just now uploaded it [link] I lined up points on the chin, forehead, etc that had an equal point on both sides of the head & calculated the degrees of the angles based on the rotation needed to realign a horizontal line to match the perspective angle shown for each "horizontal" plane of the mech's head. hope this helps to clear up what I was trying to describe lol