There's a lot of artwork for Dune out there that's been done since the book was published. A lot of it is redundant as far as the subject matter. There's always a big sandworm bursting through the surface of the desert, small, lowly Fremen used to demonstrate the scale. Dune is all about scale. The epicness of the story. The vastness of space and the amount of time the story takes to fully elapse. It's a big one, like a sandworm. The best art for Dune is the art that was created closest to the time of its publication. My favorite art to illustrate the story also has to have a bit of mystery, and drift toward abstraction, rather than photo-realism. The abstraction helps make the art less defined, less anchored in our day-to-day reality, and lets our minds fill the spaces with what could be, which is what science fiction does. The Dune works of John Schoenherr do this and also feel of the classic science fiction era from whence Dune sprang. The chunky paint application, broad fields of color, the muted rendering, the restless scratchiness of line, are all indicators of 70s illustration. They remind me of another giant of illustration who also tried his hand at depicting the deserts of Arakkis, Brad Holland.
All artwork by John Schoenherr