I've started making a few ACEOs (Art Cards Editions and Originals) and will put them up for sale shortly. Here's a preview:
ACEO No. 03
You can google ACEO to get the full story, but essentially they are miniature art cards, always 2.5"x3" -- tiny -- but can be completed in any medium. Whether they be watercolor, acrylic, oil, collage or wood, clay, fabric, and metal. Size is the only qualifier.
They were quite a fad for a bit and the enthusiasm may have slowed somewhat. People collect and mat/frame them, or just treat them the way they would baseball cards. They are fun to make.
These 3 are on textured paper, made with watercolors, ink and white gel pen.