I've got the boxed set of Alien. In some of the extras Ridley Scott talks about the heavy metal mags being quite a big influence on the style of the film. That and Ron Cobb's technical realism.
Some interesting images here
http://eggtea.com/?tag=scifi-artThe original alien before Giger cam on board:

Can you imagine how the film would have bombed with a crappo bug like that?
One that might be relevant for the prequel

Originally there wasn't going to be a derelict spaceship. The alien eggs were going to be found in a temple on the planet. I think they stole the idea for the Alien Vs Predator film. I think it would be a good bet that the prequel will feature this.
"Man will never be free until the last king is strangled with the entrails of the last priest."
- Denis Diderot (1713-1784)