Giger: Swiss surrealist rewrote the rulebook on how to design a movie monster

 

"The Alien creature was based on a Giger print named "Necronom IV", and marked a major departure from the clichéd green men often seen in movies until then. Giger's alien was androgynous, eyeless, and insectoid, playing off the artist's prior exploration of what he called biomechanical themes. Its design also had a clear sexual subtext, with its phallic head and disturbing reproductive system; the crab-like "facehugger" form wraps itself around a victim's head, impregnating it so the infant alien can burst out of the chest."

see photos of a Giger exhibit: 

'Alien' artist H.R. Giger dead at 74 | The Verge