Thanks for the link Francois. It's an interesting concept. I can see it would be helpful as a starting point to identify different formulae and get a general sense of their features.
I'm not sure that seeing a flickr image really gives good representation though - especially given the layers of digital intervention from scanning, processing then into the hands of flickr's own post-uploading-processes. I think a written description/ experience would be much more valuable, even given the subjectivity.