I have been working on the illustration for the first Alien lately. It took a bit of time but I got the sketch done! [link]
I can't wait to start polishing and colouring! My main challenge was that I really wanted to illustrate Ripley in the spacesuit, but she spent the entire final scene strapped to a chair so I took some liberties to make it more dynamic.
In the meantime, I posted a concept art featuring all four aliens from each movie. [link]