The Deacon was originally part of the Engineer’s religion. You see one enthroned on the wall mural in the room with massive Head and vases/ canisters of Black Goo. So no its not Neomorph, it has a more sacred purpose to the Engineers, “it must be something we haven’t seen yet.” (Biahop, Aliens)
I don't know about religion, so much. It may very well just be a way of 'advertising' what the end result of that particular substance and its evolution is, like putting a huge Mickey Mouse mural on the side of a Disney store. It was right there in the ampule room, after all.
My religion thesis about the Deacon came from earlier Prometheus scripts. So its fair to say that affected my judgement.