After Michael Whelan illustrated the first book in the Dark Tower series by Stephen King, his artwork became synonymous with the story. The author doesn't describe the tower in the early books of the series, but many of the main characters experience dream visions of the object of their quest. Michael offers one of his own for the frontispiece of LEGENDS, an anthology of prequels by best-selling authors published in 1999, which included a Dark Tower story by Stephen King.
(A special note: Michael substantially repainted his original in 2000, so it is different from the image that appeared in the book.)