I've collected these wallpapers over a number of years and have no idea where I got most of them. I've also renamed them all (giving them a number) so I don't even have their original filenames.
I find wallpapers in a number of different locations, but good places to check out include Imgur, Reddit, 4chan, and Twitter (now X).
Because I downloaded most of these from sites like Imgur, Reddit, and 4chan, I have no way of knowing if there is a copyright on these images.