Update 2013: These are now available in my Etsy shop.
We also made thank you notes that I thought were adorable. We saw this version of the idea here. Again, with the same theme of proficiency I added a place for the buyer's name and amount owed. I used a thin tip Sharpie to fill it in. I left space on the left side to hole punch so it could be threaded though the ribbon for the boxes that were together. This did not work out. The cards were too bulky for the tied boxes. Thankfully, the thank you note slipped easily between the ribbon. Orders that had four or more boxes were put into gift bags. The thank you note did get tied to the ribbon and those looked cute.