Recently Abbey of Abbey Goes Design Scouting posted a how-to on searches for vintage paintings on eBay. Paintings that have a vintage feel to them but are still reasonably priced...
Her advice is worth sharing. Check out her original post here.
When searing for affordable vintage painting she limits her search to between 1900 & 1949. We went step further and narrowed our search down to works of American origin. You can tweak the criteria around to your tastes but that does seem to be the "sweet-spot" for some good inexpensive finds (mixed in with some more pricey works).