How the Heck could David have created the Alien when there's already an Alien on the murals in Prometheus...........Aaaaaand here we go again!
To be fair, it's an Alien, not The Alien.
It's a deacon, and yes there are creatures resembling facehuggers, apparently doing what facehuggers do.
So it all may not be a case of David creating the species, but merely improving upon the design.
Nevertheless, I concur that there is a deacon and proto facehuggers on the large wall. This predates David's experiments by at least 2000 years. It's right there, on film, and I won't say it isn't.