With the DNA sequence starting off the prometheus movie, I somehow wonder what kind of a film we would have had if they had spent time developing another alien form: something completely new, original and terrifying like an alien resembling the DNA shape itself. It does sound quite bizarre, but it could have had limbs or a proboscus that resemble a crude DNA shape that unravels to reveal tentacles with snapping teeth or something.
Without it ending up too much like "The Thing", it could have been quite horrific yet beautiful at the same time, making the prometheus crew want to get up close and personal to investigate before it turns on them.