Do you need an image that's already got copyright clearance? Consider the venerable Pictorial Archive series from Dover Publications, a rich source of public domain illustrations, graphics, typefaces, and design of all kinds. Here are the covers of just a few representative Pictorial Archive titles.
Hayward Cirker (1927-2000), the founder of one of the quirkiest publishing houses around, was a connoisseur of graphic design who had deep pockets and a singular vision. (I know. I worked for him in the early 1980s on the production of the Pictorial Archive series. I've included a bit of the firm's history below.) Cirker used to buy rare illustrated books at auction and turn them over to an artist who would select the best imagery and arrange it for faithful reproduction in an inexpensive paperback Pictorial Archive edition.