I'm looking at the high res version of the picture (albiet not the one that has been brightened up significantly) and all I can say is while the shape has some familiar elements to it no one can say for certain what it is. Based on the flashlights shining on it we can def. say that the textures are reminiscent of the egg from Alien, however the details at the bottom and some of the shadows make it seem like it could easily be a head. The shape is one of the things that throws everything off... it's too round to make me think of a head or an egg. If it's an egg it's obviously not like the oval eggs we know. The space jockey's head in Alien was somewhat round but this looks like almost a perfect sphere. The proximity to the body and the angle allow for guesses that it's the head, though like mentioned the decapitation seems strange? There is nothing like it in the other pictures which is weird because eggs have always been found together before.
I will say the low-res trailer cut does appear to have the item we are discussing with something "bursting" out??
