And while there is understandably an abundance of material directly related to New York, there are artifacts from around the globe as well, including Russian Civil War posters, Renaissance Manuscripts, and, "A Suite of Twenty Engravings of the Yuan Ming-Yuan Summer Palaces and Gardens of the Chinese Emperor Ch'ien Lung" (published in 1786).
The Gallery also boasts a bit of 'pre-NASA NASA' - with some early celestial maps and illustrations from the 1596 publication, "Prodromus dissertationum cosmographicarum continens mysterium cosmographicum, de admirabili proportione orbium coelestium, de que causis coelorum numeri, magnitudinis, motuum,que periodicorum genuinis & proprijs : demonstratum, per quinque regularia corpora geometrica" - which presumably translates to something roughly like, "Astronomy for Dummies."
A sampling of other collections includes historical maps, George Caitlin's North American Indian Portfolio, Goya's "Disasters of War" and the Miss Frank E. Buttolph American Menu Collection, 1856-1930. ("Menus?" you ask? Well let's see your hobby immortalized at the New York Public Library along with the works of Copernicus and Goya.)
If you still can't find what you're looking for, check back later - the Library's plan is to use twice monthly updates to increase the size of the collection to 500,000 items within the next few months.
And while even such an impressive collection might seem to be of little more than passing interest to most of us outside the scholarly community, the traffic-generated shutdown demonstrates that, in fact, most of us simply like looking at old stuff - especially if it's old stuff we don't usually have access to. Naturally, navigation needs to be efficient in order to keep us visitors on a site of this kind, and the Digital Gallery has a multitude of methods which allow us to wade through the collection or zero in on a specific image.