I'm a pretty big fan of H.R. Giger, as are many artists. His style was and is so unique that it constantly gets copied, yet never topped.
One of Giger's trademarks is lots of sexual imagery, so one of the things that I guess you could say he influenced me on is using a lot of that in mine as well at times.
I think creatures get creepier the more disturbing parts you add. Twisting and morping the human body is a good way to turn a stomach, and what better way to do that, than by adding a big vagina in the middle of your creature!