The reverse side of the packaging once you get it open has an interesting history:
What are artist trading cards?
Artist Trading Cards (ATCs) are miniature pieces of art that are traded around the world. Artists create, trade and collect art at organized "swap" events, either in person or online. It is a great way to meet other artists and share your work. The only official rule for ATCs is the size: 2.5" x 3.5".
How did the movement start?
In 1997, M. Vanci Stirnemann, a Swiss artist, created 1200 cards by hand as a part of an exhibit. On the last day, he invited others to create their own cards and trade with him during the closing reception. After that, the movement took off as other artists organized major "swap" events! Today, there are ATC swaps in almost every major city around the world. There are also many online swaps.
There's more info here if you're interested: Strathmore
I'll post any that I make, maybe I'll do one tonight!