Here are a couple of gift boxes and cards I made using the Decorative Packing Tape from Fancy That! It's just like a roll of regular packing tape, only WAY more beautiful; the tape itself is colored and the designs you see in white are clear. I think it would be cool to decorate boxes you're going to ship. How fun would it be to send someone special a fancy box in the mail?
You might even brighten the day of the clerk in the mail room.