ATC's or Artist Trading Cards are small collectable and tradable works of art. Each one measures roughly the size of a baseball card, 2.5"x3.5". It is based on mail art and originated in Switzerland. They are made from almost any medium - watercolor, acrylic, collage, pencil, ink, metal, fabric and are typically exchanged. In the case that they are sold, they are called ACEO Artist Card Edition Originals.
Cards can have any theme, color, or idea. They are miniature pieces of art that people and people like to communicate and exchange them with other artists. If you don't have an artist in your area, check out ATCS FOR ALL for other artists interesting in trading.
I spent the morning Gelli-printing and came up with some fun backgrounds. I took 8 and made them into a single page that you can download and use as backgrounds for your own ATCs. Here is the link to the download. Save the file to your computer and print. Then, cut out the images and use to make artist trading cards.