In 2008, the British Library, in partnership with Microsoft, embarked on a project to digitize thousands of out-of-copyright books from the 17th, 18th, and 19th centuries. Included within those books were maps, diagrams, illustrations, photographs, and more. The Library has uploaded more than a million of them onto Flickr and released them into the public domain. It's now asking for help.

Though the library knows which book each image is taken from, its knowledge largely ends there. While some images have useful titles, many do not, so the majority of the million picture collection is uncatalogued, its subject matter unknown.

Next year, it plans to launch a crowdsourced application to fill the gap, to enable humans to describe the images. This information will then be used to train an automated classifier that will be run against the entire corpus.

The library is also soliciting ideas for how to present the collection to aid the tagging and metadata generation, and also make the pictures easier to navigate.