Quote from full announcement http://britishlibrary.typepad.co.uk/digital-scholarship/2013/12/a-million-first-steps.html

We have released over a million images onto Flickr Commons for anyone to use, remix and repurpose. These images were taken from the pages of 17th, 18th and 19th century books digitised by Microsoft who then generously gifted the scanned images to us, allowing us to release them back into the Public Domain. The images themselves cover a startling mix of subjects: There are maps, geological diagrams, beautiful illustrations, comical satire, illuminated and decorative letters, colourful illustrations, landscapes, wall-paintings and so much more that even we are not aware of.

Flickr account http://www.flickr.com/photos/britishlibrary
Example of image http://www.flickr.com/photos/britishlibrary/11307195524/
Example of all images from a book http://www.flickr.com/photos/britishlibrary/tags/sysnum002660292
Stuff for coders https://github.com/BL-Labs/imagedirectory

So... :-)