One tool I wrote and I wish I would still have time to maintain was "Folders2Flickr" (luckily someone forked it https://github.com/richq/folders2flickr and keeps it alive). It's basically a DropBox for pictures with Flickr being the storage server and viewer. The tool simply synchronizes all of your pictures which can be in a hierarchical folder structure and recreates this folder structure on Flickr (but uses Sets/Albums instead of folders). I dont see the stats now but for years it supplied Flickr with multiple pictures every single second 24/7 from many users.