This past session, the PCs traveled through a gate that ended in a domed chamber with a field of stars painted on the inside of the dome. The building below depicted scenes of the city, but with six-fingered hands (a game theme) painted on to them later.
Queue up questions about the stars - how much celestial drift do they show? Are they accurate? Do they match the stars in the northern sky? Any stars bigger than they should be, or brighter? Is there a "North Star," and if so, is it properly depicted in relation to the other stars?
The murals? Questions have come up about the relative height of depicted figures, details on their weaponry, dress, facial features (recognizable individuals), etc.
I see this in player's questions about art in general, actually - the questions assume three-point perspective, representative drawing, Vermeer-like attention to color changes, deliberate attempts at photo-accuracy, etc.
But in most cases, this isn't that kind of art.
As a result, I've been trying to make it clear that art isn't usually Renaissance and post-Renaissance realism. I point out medieval and ancient approaches to art. Things like lack of perspective. Centrality of image meaning centrality of importance (aka Jesus is drawn in the middle). Symbols and signs used to show meaning ("That guy with the ankh is a priest, but that guy with the sword represents justice"). Gaze direction meant to show relationships. Specific location of objects or figures in a picture may depict multiple events over time, or be placed as part of some kind of artistic standard, much like how people sign things in the upper left hand corner or bottom right - it could just be convention.
Images made for a purpose are not always made by a master painter, either. They often are, but not always. Large images will have been made by crews of artistic assistants supervised by a master, if there was one. Hand-drawn art by people without Artist skill may lack accuracy and merely give a sense, much like how stick figures suggest but don't really accurately depict humans.
With that in mind, while art can and should be examined for clues in my game, it's often examined with a modern eye used to photo-realism like that scene out of Blade Runner. Instead, it should be looked at for meaning, not precision, more often than not.
And I'm doing my best to get that across in a way that allows the players to sense what is generally there to find.