After a few weeks of scouring the internet and the Internet Archive for every web page who's existence I could discover, I've found a bunch of lost complete scenery sets that haven't existed as their own (or any) download in a decade.
First, the complete Hollywood Letters, and numbers, and question mark and exclamation point!
Thanks. A lot of what I've found is either low quality or already in the database. (Fisherman's awnings, for example.)
This link covers a lot of stuff, including the complete LOTR and Hairy Potter stuff and parks. All of the download links work by the way, it seems somebody went out of their way when they heard the site was going to close to put every single download and download page on the Internet Archive. (Thanks, Somebody, you've saved a ton of stuff for posterity.)
This site has various useful things, including glass walls, waterfalls and water features, and some various Superhero stuff NOT including what I've been looking for. A few of the download links don't work, and much of it is (I "think") already in the database here.