Watch the blueray its easier to notice. The skull has always been there in Alien 1979. The skull is coated with a semi translucent material and you can only see it directly in direct light conditions. For instance:
Love that big guy (the one with the skull on his shoulder) :), thanks for sharing Leslie! To give some feedback though, I think his skulls can use some more volume ;) Keep them coming
Hello guys here is a sculpt I did in Sculptris, it was my first attempt at the program. I was really impressed by it. I used a combination of a regular human skull and a peruvian skull. Comments and Feedback is welcome. I took it in zbrush to make some quick renders. Thanks.