I've shipped 100's of flat prints 13x17. I just sandwhich them between 2 pieces of cardboard with tissue paper on the surface to protect from scratching. I've never had one damaged. But you must do Priority mail.
Framed prints are a different story... I would suggest shipping them in a refrigerator box full of pillows. I think postal workers mistake "fragile" with "catch."
..of course the cement box method works too... way too heavy to throw.
