I’ve only now just noticed that the Struzan ROTJ art has ESB’s Luke and Vader duel (complete with blaster on hip and a blue blade).

Something else to keep in mind about the Struzan artwork is that all three covers are a collage that fit together into one big image. You can tell with the starfield between the three images that the middle is ESB and the stars are moving out towards the left on the ANH cover and to the right on the ROTJ cover. That’s why no characters are repeated across the 3 covers (except Luke and Vader dueling obviously), which kind of explains why Palpatine is on the ESB cover. ESB has all the bad guys, ANH has all the good guys, and ROTJ has the random leftovers.