Ridley is smart so what clues has he left??

I am not trying to over think anything here but the face statue room left us with something I have been pondering. You enter through a massive door only opened by the correct finger presses only to walk through hundreds of urns to confront a massive statue. How many visitors other than an android would be able to read or decipher what code was needed to open this door. A mural is above depicting what can only be taken as an engineer hovering or standing over a dog faced creature hunched over. You keep on walking behind the head statue to see, only briefly in the movie, a picture of a xeno. In front of this xeno is a rock table with a green crystal superimposed into it. This green crystal has something of value or significance for future films IMO. Why??? Green Goo was found on one of the opening devices in the cave tunnel david opened. You now have Green Goo and Green Crystal and interestingly enough the green goo looked like Xeno saliva only it wasn't clear from previous movies. David spread it between his fingers and it shared many common characteristics xeno saliva has. Also, the green goo between davids fingers seemed elctrically charged. Enough about the xeno for now but what significance does this green crystal have and why a xeno picture behind it. IMO, the engineers worship whatever xeno was depicted in that room which is likely why they had it at the end of the room and perhaps the green rock represents what planet or element it comes from. In any event, something other than the Prometheus crew and Engineers have been there. What else rocks a green goo with them wherever they go. Also, Could this green crystal be a valuable resource or form of power. Thoughs??