I'm now at a Release Candidate stage, as far as the actual images are concerned.
http://vectorpoem.com/lucasarts_backgrounds
Lots more work compared to my last update, here's what I can remember:
Finished up images for the remaining games, eg the palette shift rooms in Zak256.
Integrated all the costume-based parallax objects I know of: the Mansion interior in Monkey1, the Woodtick boat wreckage in Monkey2, and several in Fate of Atlantis (New York, Azores, Crete, Algiers, Atlantis). And one I found in The Dig.
Did a file rename pass to replace all my 001_snake_case_style_names.png with easier to read names with capitalization and spaces, retaining the room number for its historical meaning.
Renamed the game and version directories to be similarly more human-readable, eg "Commodore 64", "DOS EGA", "Windows", etc.
Added and edited several more images I realized were missing or inaccurate when I was doing this big renaming + quality control pass.
If anyone spots any inaccuracies, omissions, or otherwise at my temp archive link there, now's the time to call em out. Besides that, I just need to finalize the readme file and decided on a format for it (plaintext, markdown, HTML) - this is probably something where I should browse archive.org for the better put-together collections and see what they did.
Thanks again for the help in getting this together! Serge and the rest of yall definitely get a credit in the readme, along with all the tools I used.