The meaning of the mural, another unaccounted for organism? - A way out theory

Is there a chance that there is another organism that is grown as the suit for the Engineers? The mural we've all seen depicts how the Engineers take on this organism and effectively "Shell" it from the suit and wear it to obtain their god/king like power? Hence the being on the left is in a subservient pose? It also looks a little like the direction of Fifields mutation perhaps? These "King" engineers are then entitled to a place in the sarcophogus. This lends to the cloaked - and what I assume naked - engineer at the waterfall, sans suit for some reason Maybe the temple is a breeding ground for these other organisms, with the "graveyard" of failed organisms they come across...and they turn on the Engineers suddenly? Take this with a pinch of salt by all means (it's 2.45am here haha!)