Sometimes, a blast from the past can be just the thing to get your design wheels turning. Here are some links to advertising, and photographs from long-ago eras, plus a bit about how the poster got started.
The History of Posters -Background of poster typesetting and production (they had to use wooden type for larger type sizes), plus some marvelous illustrations as examples (thanks Mary Louise Penaz for this link).
Wacky stuff – A personal collection of ephemera on Flickr (thanks to +Isabel Fortin for the link and the inspiration for this post).
Duke digital collection – Early advertising in America from 1850-1900, and some of those brands are still around.
Library of Congress Memory Collection – Transportation – Photographs from the world’s transportation commission – railroads, camels, elephants, sleds, horses, and even sedan chairs.
(Some of these are public domain, some not. Check before you use any of them directly).