I found this great vintage hammer artwork, and used just a crop of it slightly askew on a fold-over card made from an 8.5x11 cut in half and then folded. (By the way, I recently discovered the most amazing matte photo paper and it makes fantastic cards, too since it feels nothing like photo paper, yet prints like photo paper. It's by OfficeMax and it's their Matte-Professional).
This card was for a builder client and to me the personal, handmade quality makes it more special than anything store bought. And they are so easy to make!