just to take this a little further off topic,
Here are two long murals in museums.
Both of these are from the National Museum of the Marine Corps.
This one uses the background image as a hook similar to a tradeshow hook. It grabs your attention from across the room to draw you into the space. Then the titles bring you a little closer. Once close enough to read the text, the mural image is no longer important.
This second one, the image is just used as background. The imagery isn’t really important in the sense of conveying pictorial information (other than time period) and only lends atmosphere and a sense of place to the timeline that is on the face of the mural.
The timeline itself is text heavy and the photos would be a much higher ppi than the background mural.