A few nice photo to poster images I found:
Uncle Sam I Want You - Poster No Words
Image by DonkeyHotey
See the complete Uncle Sam Series - Set
The source image for this illustration is from a World War II poster titled "I want you for U.S. Army," designed by James Montgomery Flagg for the U.S. Army and available via the Library of Congress.
This image has been enhanced and cropped to make it more useful for your graphics projects.
