Bookofjoe pointed out that the New York Public Library now provides public access to their digital image repository:
NYPL Digital Gallery provides access to over 275,000 images digitized from primary sources and printed rarities in the collections of The New York Public Library, including illuminated manuscripts, historical maps, vintage posters, rare prints and photographs, illustrated books, printed ephemera, and more.Wow. It's been a while since such a large repository has been connected to the web. It reminds me again how far we've come since Paul Kleeberg first showed me the minutes of a city council meeting in Australia using a Gopher client back around 1994. Even so, we're only at the start of this journey.