In ROTJ, where the smoke from Vader's funeral pyre rises up to meet the fireworks, the image breaks up.
Sorry I don't know all the jargon -- "pixellization" ? "encoding error" ? -- it looks yucky for an instant.
The bonus disc has the still image galleries outside of the DVD-Video zone, and within the DVD-ROM zone.
Farsight's still image galleries are visible on a computer, but not as slideshows on a standalone player (unlike Dr.Gonzo's bonus disc.)