There is a couple that have three Aussies who frequent the dog park we go to. They have one of each size. A large one, a medium one and a small one. I'm guessing that maybe the smallest one is a teacup?? I'll try to remember to post pictures of these guys when I get home.
Tyson, the smallest one, is a riot! He gets super excited and just wants you to throw a ball ALL day long. He also likes to jump in the 5 gallon water bucket for a cooling off and rest from running himself ragged after the ball. That should give you an idea of his size.

Will come back to post pictures.