I'm definitely pro-skull, but I like when it's somewhat vague, seen only when You get a gloser look or under certain angles. It's perfect with Stompy from Isolation, or Protomorph from Covenant. But I don't like where it is too visible, like with Drone design in Fireteam Elite. For me barely visible skull adds to creepines of Alien, when at first You look at faceless gaze, and then You realize that there is something behind it, but something no less disturbing than lack of eyes; Two empty eyesockets. And it gives indication that maybe it is something Alien, but it came from us, twisting ours own biology for its purpose. Besides it's original design for Big Chap, even if You don't see it in the movie itself.