Known as aceo's, they are 2 1/2 in. by 3 1/2 in., pretty cheap, and collectible.
Mr. P, blind as a bat, has been helping work on one. I tell you, I have been rummaging through the fabric stash, among other places, to find all the right colors. Somehow, aceo's seem more doable than larger works. The reality, of course, is that they can take as long, and certainly take as much planning and design as a larger work, I think.