Check out this free resource.

NY Public Library Digital Image Gallery

I typed all kinds of things into the search ("art deco", "art nouveau", "advertisement", "bauhaus", "african") and was rewarded with sensory overload.



There are even old stereograph (first 3D) images for the photo history buffs:



I started thinking some of the old advertisements could be an inspiration for a web design layout.  Like this one:



Obviously not exactly, but I can see it.  Feeling pretty inspired....