post, I googled "Frank Frazetta The Dancer From Atlantis" and found the attached image which seems to have the book cover in question in the background.
I have found some good book covers to illustrate blog posts. I agree that the cover of a novel should show a detailed accurate scene from the text, like a film frame or comic strip panel.
Poul Anderson's Time Patrol series is complete in two volumes, Time Patrol and The Shield Of Time. Each of these volumes has a cover that includes the detail of the Time Patrol symbol, an hour glass in a heraldic shield.
Bruce Pennington, cover artist, commented in the blurb on the back of Anderson's The Day of Their Return (London, 1978), "A book with plenty of pictorial content for at least a dozen good cover illustrations..." and provided one such illustration on the front.