Claw on the cave ceiling

It could be the part where we see the Xeno Murial..... But we just dont know untill we see the movie, but that is potentialy what could be happening. Maybe its a warning?

Didn't Ridley intend to have some sort of 'spores' being stumbled accross by the crew in the original Alien. In an interview it has also been stated that this is what would have happened to the crew of the Nostromo if they had stayed on the Derelict.... Could the Engineers species be waiting for humans to stumble accross them to release their spores so that they can feed on the humans and grow, or use the humans bodies to develop, etc??....

Yup! Xeno hand. Note the double fingers :-)