I mentioned Mssr. Jaquays in passing a couple days ago. This guy did it all. He wrote what many consider some of the best dungeons ever created (Caverns of Thracia and Dark Tower from Judges Guild), edited gaming magazines (Dragon and Dungeoneer), plus he was one hell of an illustrator. Check out these fab Dungeoneer covers.
I love the yellow robot in the lower left. He looks like C-3PO after he retired and let himself go. Check out this close-up:
(Incidentally, this little guy was the inspiration for Unit BX-652, a character sketch I wrote for Dr. Rotwang's awesome RPGsite thread about 'Casablanca in Space'.)
Here's the great spaceship cover for issue 12. Here Jaquays really shows off why the folks at GDW chose him to do the spaceship art for Supplement 9: Fighting Ships.
That background is absolutely fantastic. I want to be on that ship, heading into that nebula. That's the exact emotional effect I want to get from this type of sci-fi art.