Would it be possible to search by a thumbnail's number ?

I'm untangling a slide-mount archive of old zip-files, many divorced from their thumbnails. Okay, a lot are obvious, many can be matched by a process of elimination, but there's a bunch left over.

Sometimes Google Images can identify them. Sometimes, I just look at an image, eg 89574.png, and mutter 'I'm SURE I've seen that, but where ??'