keep in mind that most chestbursters have yet to "grow" their back tubes. It's not even known if we'll ever see that particular creature again since Shaw heads off into the sunset towards another planet. That was probably some extra cheese thrown in for the fans. Not that I wanted to see that much cheese...
I'm kinda happy that this xeno was not just gratuitous and that something was set with the mural about him.
That creature is important to the Engineer, they have an altar with a mural featuring it.
We are definitly going to see it again if there is a sequel.
Lets not forget that the movie originally ended up with the survivors fighting the same creatures but fully grown.
I have yet to confirm if they were born from the surviving Engineer or were those that were born 2000 years ago when the outbreak took place.