[Revisit] SF Stories written for paintings

There was a somewhat recent question (thread?) here asking about SF stories written for already-existing paintings. Last night, I ran across a reference to such a story.
I’m slowly progressing through the Poul Anderson collection “Kinship with the Stars”. Poul gives a neat little introduction to each story, and one of the intros[1] says the following:
“Often in the old pulp days, an artist who had nothing else to do at the moment would turn out a painting, which he would then sell to a magazine editor for use as a cover. The editor would thereupon find a writer to produce a story incorporating the scene. Occasionally  the whole thing was so preposterous that just explaining it away generated a plot. However, the premise did not necessarily lead to bad work. In fact, the first story of mine to win a Hugo Award had such an origin.
…”
Digging around, it seems he is referring to “The Longest Voyage”, and I would (slightly less-confidently) guess the painting/cover is seen at
https://en.wikipedia.org/wiki/The_Longest_Voyage
Tony
[1] The intro for the story “The Critique of Impure Reason”.[2]
[2] Note that “The Critique … ” is not such a story, though it’s adjacent, since Poul goes on to say:
“At another time, being in a mood to write something short but without an idea that caught my fancy, I said to my wife “Tell me a cover”. She thought for a moment and replied “A man sitting at a desk, worked to death, while a robot lounges beside him smelling a rose”. Ah, ha!”[3]
[3] So his story “The Critique of Impure Reason” was written for an imaginary painting described by his wife.