Cinemart have just posted up what seems to be two new images of an actual prop used in Prometheus. According to their studio source, this prop is a prosthetic mask designed specifically for an actor to wear and described as the face design for “the alien”. Which certainly looks like the Space Jockey seen in ALIEN. You can read their own description of the mask below.
“The prop (organic looking design), in mould stage (white coloured), is a human skull with large eye sockets (slightly apart than normal) and what looks like another layer of bone having grown over it. The extra layer is in the form of what we know as the facehugger (without the legs). There is a trunk-like nose where the creature’s tail would naturally be in this position (or the appendage underneath used to lay the egg into a recipient). The prop is a prosthetic mask without makeup added, but the insider also said the creature featured in Prometheus has been executed with very little CGI planned. The appearance of the mask is of a human skull with facehugger frame on top.”