I just saw the news that artist Ralph McQuarrie passed away yesterday at the age of 82. His concept paintings for the Star Wars trilogy were George Lucas’s guiding force for the look of the films.
I first saw McQuarrie’s work in The Star Wars Album, a “making of” book published in 1977. His concept paintings for A New Hope inspired me to draw and eventually pick up a brush and paint.
A few words from George Lucas and a slideshow of McQuarrie’s work here; a gallery of his Battlestar Galactica concept paintings here.
Fante's Inferno 
I have an entire collection of trading cards based on McQuarrie’s artwork. The rendering of C-3P0 is so much like Metropolis, it’s freaky.