From what we see it
Prometheus and what you explained in your post :
Then :
From what we learn in
Alien :
So how is the egg created ?
Yes , this infected creature will lay infected eggs containing facehuggers, the same way infected Holloway and Shaw gave birth to the trilobite !
Note that this creature is very similar to the usual xenomorph (thorn on the elbow, excrescence near the shoulder...) but hasn't got the penis head.
I know it is difficult to distinguish the thight but the iliac crest is visible and it may go downwards, that's why I think this PRE-xenomorph creature infected by a trilobite would give birth to the mural crucified creature
Many people wonder if the goo is made by alien DNA or if xenomorphs are created by the goo. My explanation is the latter option, Damon Lidelof hints it
here, also in the audio commentaries of the movie.
Now will Ridley stick to that for the sequels is another story.