The Library of Congress has some great stuff and some pretty boring stuff. You can easily get lost in its massive collection which takes a great deal of skill to navigate. However, I came across these posters from the WPA project which are pretty fantastic.
All images Library of Congress Prints & Photographs Collection
Ground Glass 
This Pet Show poster is great. For all of the pet lovers this really epitomizes the loving energy of a good pet as well as that look that says,” Who me!”. This is one I would put on my walls. No pet at the present time and I wouldn’t have to feed or water these cute dogs.