Time travel through millions of historic Open Library images with the Internet Archive's extraction of more than 2.6 million images on Flickr. I have written about this before, but I thought an update would be helpful. Nearly all of these images are in the public domain. The images come from a process of OCR examination of the 600 million pages of library books scanned by the Internet Archive (Archive.org). For more information, you can see the BBC News Technology article "Million of historical images posted to Flickr" and the Open Library Blog post entitled, "Time travel though millions of historic Open Library images."
It might also help you to know that the Open Library is a part of the Internet Archive.