Artist Joe Corroney has created some awesome pieces of art for comic book covers and other things. Subjects like: Trek, Star Wars, Farscape, and so on can be found at the link below. Here's a little sample. Awesome stuff!
http://www.joecorroney.com/cgi-local/imageFolio.cgi (http://www.joecorroney.com/cgi-local/imageFolio.cgi)