Also, Ridley Scott spoke to Movies.com and was very open about discussing specifics about the Engineers. Here are a few excerpts:
So I always had it in there that the God-like creature that you will see actually is not so nice, and is certainly not God. As she says, "This is not what I thought it was going to be, and I think we should get the Hell out of here or there won't be any place to go back to."
Thatís not necessarily planted in the ground at the tail end of the third act, but I knew thatís kind of where we should go, because if we've opened up this door -- which I hope we have because I certainly would like to do another one Ė I'd love to explore where the hell [Dr. Shaw] goes next and what does she do when she gets there, because if it is paradise, paradise can not be what you think it is. Paradise has a connotation of being extremely sinister and ominous.
When asked about how he planned to approach the film to pull audiences in, Scott spoke about the beginning of the film: "I was hoping I had with the fact that you have a sequence at the beginning of the film that is fundamentally creation. Itís a donation, in the sense that the weight and the construction of the DNA of those aliens is way beyond what we can possibly imagine."
There is lots more to be found in the interview here.