Here is a simple and easy way to use up some clay pots that are too small to plant in ... create a pot stacker. They look great among the tall plants of the garden. I hammer a metal rod into the ground, pair up the clay pots in the same size, add them rim to rim to cover the rod. I even added a plant in the top pot. http://craftygardener.blogspot.ca/2012/06/pot-stacker.html
Oooh. I have a bunch of too small pots waiting for soil and plants to call them home. That sounds like a nice idea.
If I can get to my little pots before my daughter decides to claim them then I'll give your idea a try.