Eleanor Ehrhardt (uncredited), Star Wars: The Maverick Moon (Random House, 1979).
Illustrated by Walter Wright.
Star Wars: The Empire Strikes Back Japanese promotional flyer (chirashi)
This originally took place on Had Abbadon (Coruscant) before it became Endor. In one early draft, Luke joins the Emperor after killing Darth Vader, but in a ruse, points the one Death Star at the other one, killing the Emperor. This image may depict that early plot point.
Ralph McQuarrie concept art
Boris Vallejo’s The Empire Strikes Back posters