Someone dropped me an email asking why I don't distress these designs. They're intentionally clean in order to make customization easier. You can always degrade an image, but it's impossible to clean up one that's been aged. With a basic image you can bleed the line work to give a more hand-drawn appearance, layer on texture, and hand color the design any way you want. Here's an example using the image above.
This took about ten minutes to do in Photoshop, but you could do it equally quickly using something like GIMP. Keep in mind that I'm a hack with no real natural talent. Someone who actually knows what they're doing could do a far better job in the same timeframe.