Great observation, Kevin! But yes, this is one of several such callbacks across episodes, that are featured in the Columbo Scrapbook article on this site, "Columbo Flashbacks" -- it is number 5 in the collection:
And long after the Scrapbook article was done, a post on tis Forum pointed out that a painting by Sam Franklin in "Suitable for Framing" makes an appearance on the wall of the hospital waiting room in "Exercise in Fatality. You can use the Forum's search feature to look for "Sam Franklin Painting" for details, although unfortunately the links for the images are expired.