UPDATE 5/27/19: Looks like these features are no longer available.
Flickr has something called “interestingness.” I don’t know if this is new or I just never noticed. A photo gets included based on “where the click-throughs are coming from; who comments on it and when; who marks it as a favorite; its tags” and other stuff. You can spend hours on interestingness so don’t go unless you have some time.
Not sure why, but there’s a calendar view in case you wanted to see interesting photos from June, 2008, for example.
This isn’t new…. it’s been around for as long as I’ve been using flickr. When searching for slide photos, I always sort by “interestingness” first. That’s where you find the really cool stuff.
Only if the “interestingness” filter fails to find something useful do I resort to sorting by relevance.