>Well for adult bikes you are pretty much fixed at 700C. If making a bike pedaled contraption not so much.
For racing/road bikes, maybe. You're leaving out the 26" wheel adult bikes (which over time has encompassed 5 different rim diameters[1]) and 24" wheel bikes that are targeted at youth, but smaller adults sometimes prefer (well, those that have been give the option).
My bike pedaled contraption is a rear suspension compact long wheelbase recumbent with two real 20" (406mm rim) tires and they're spectacular.