I don't see any significant resemblance to Ryan. Anyway, the timing's a bit iffy. The book's publication date was August 1996, which means the cover art was probably done months earlier. And Dark Skies didn't premiere until September 1996. So would promotional photos from the show have been available early enough for the cover artist to see them? It's possible, but I'm not sure it's likely.
Also, I think the face that reminds you of J.T. Walsh is meant to be Jimmy Hoffa. There is a resemblance between them.
Well, I've illustrated a few books that came out a week or so after my work was completed, but I'll grant that that's probably far from typical. Even so, I don't think it's impossible that photos promoting Dark Skies were available months before its premiere, giving the artist enough time to see them.
I assumed the guy on the right was Hoffa. I mean, here's an image of Walsh; I feel there's a definite resemblance: http://behance.vo.llnwd.net/profiles...ee592683c4.jpg
Though I remain fairly convinced I'm correct in my assumption that the artist based his renderings off images of the actors and just tweaked enough details to make it not entirely obvious, it's not outside the realm of possibility that I'm way off base here. If so, again, I'm sorry for wasting people's time with this tripe.