This question about repeated images in various editions of the Dungeon Master's Guide has this answer that's good (and probably right) but that would be vastly improved were it to include the actual illustrations. Usually, I'm a begging-for-forgiveness-is-better-than-asking-for-permission dude, but it's my question not my answer, and I didn't want to suggest to the answer's writer to include the illustrations without making sure first that their inclusion is okay.
In short, for the purposes of critique, comparison, or review, is including illustrations in a question or answer acceptable?