you could always make a custom one: https://arandomsite.neocities.org/blog/custom-neocities-thumbnail/
I added the recently rediscovered *original* version of my article in the library! The version that has been there was edited for republishing by some Korean tech blog. I also added Yesterweb.org to the button collage because they added a link to the aforementioned article directly.
Oh so Neocities doesn't like HTML in comments. Understandable. All you have to do is add something like ?v=1 to the end of your URLs. It just has to be question mark, thing equals value.
The browser treats that as a new url and so it doesn't use the old cached copy.