The problem with most of the vintage art people buy on the Internet and hang on their walls is that all the pictures are all the same. You know at least two people with that French chick on a bike with her hair and dress all flowy, or that black-and-white shot of the Brooklyn Bridge. God save you if you bought a Pernod ad. And if you do find a poster you haven’t seen in half a dozen dentists’ offices, it usually costs a couple hundred bucks. To the rescue comes another entrepreneur with an obsession. David Hall, on leave from the Style desk at the Washington Post, goes hunting for cool images in the databases of various public domain image archives. Then he “futzes around in Photoshop” to improve the tone and contrast and sells prints through four online storefronts, all out of his home base at the Juniper Gallery in Fairfax. The sites: for vintage images of cars and kids culled from 1950s; for vintage photographs and poster art from the Library of Congress; for reproductions of fruit-crate art; for prints of drawings and schematics from the vaults of the U.S. Patent Office. Printed on fancy French paper and mailed in a tube, the most popular image sizes go for anywhere between $15 and $50.