This is the “ur-couch”- Ajax 1990, although I have earlier examples but it is as good a place to start as any. You can think of it as an empty stage, awaiting the actors in the wings. It functions as setting and also as plot, because of the way it arranges the actors and influences their mannerism, shape and behaviour. Certain things can happen here, and we arrange ourselves accordingly.
As a picture trope it may no longer make sense, since the ubiquity of picture taking with phones has made the “formality” of posing on a couch to acknowlege a moment an anachronism. I have another posing trope, “person leaning against car in driveway” which may also belong to another time when there were only so many frames on the roll. That being said, I think the trope still has power and can be surprising despite it’s seeming banality.