"Hannes Bok, pseudonym for Wayne Woodard (1914-1964), was an American artist, as well as an amateur astrologer and writer of fantasy fiction and poetry. He painted nearly 150 covers for various science fiction, fantasy, and detective fiction magazines, as well as contributing hundreds of black and white interior illustrations. Bok’s work graced the pages of calendars and early fanzines, as well as dust jackets from specialty book publishers like Arkham House, Shasta, and Fantasy Press. His paintings achieved a luminous quality through the use of an arduous glazing process, which was learned from his mentor, Maxfield Parrish. He was the first artist to win a Hugo Award." - quote from Centipede Press
Some of the above artworks were found at Golden Age Comic Book Stories.
Additional information can be read about Bok at his Wikipedia page.