Also interesting is this remix by Brian Foo of NYPL Labs that provides an interface for searching by color, dates, genre, or color. The usability leaves something to be desired, not the least of which is performance. Ideas for improvements come to mind immediately. Of course, the remix is only as good as the data, which seems to still be somewhat spotty. If you're a techie (or even a wannabe like me), see the source code (mostly Python) for the remix on Github. I'm tempted to try my hand at it. The data is here, and the API.
Yes, more than 1,000,000 images! You can get it in a steady stream via the The Mechanical Curator, a Tumblr blog which hourly posts randomly selected small illustrations and ornamentations. Or you can dive into their Flickr photo-ocean — I know that Flickr calls it a photostream, but in this case it's an ocean. It's organized by album (e.g., musical instruments, architecture, children's books, cycling, technology, ships ...).
The search function is not as helpful as it could be -- keywords such as "batarde", "manuscript book", and "Netherlands" failed to turn up this image. I found it, instead, by scrolling through the album entitled "Images Online: a selection".