Go easy on the big fella. He did ~300 paintings and my search found some that puts the "hit" in Hitler, but in sizes appropriate for printing greeting cards or smaller, which does seem like a great idea too though. None of the typical high res providers got love for the man, but an actual thorough search should come up with more than I found. Sometimes /pol/ has an art thread where people post high res scans of paintings, would think that would be a good place to find Hitler's best stuff.