Since 2006, my artist friends have been making ATC (Artist Trading Cards) 4 times a year. June, our facilitator picks 4 themes and we make 5 cards based on the theme she picks (1 to keep and 4 to trade since we have 5 people in our group). In 2013 the themes have been, Games People Play, Architecture, Spread Your Wings and coming up - My Cup of Tea. The cards are small - the size of a baseball trading card - 2.5 x 3.5 so they fit into standard plastic sleeves. It's amazing how 5 people can create totally different art inspired by the same theme and it's fun to trade and collect them. They're little art gems.
Here are my cards for the Spread Your Wings theme. Each is a little different because I used a paper napkin that I spray mounted to card stock and cut up.