Everyone loves foot rings! This photo from e-yakimono shows just how varied the Kodai or foot ring can be.
Some of the most interesting and dynamic foot rings that I have seen are by Cory Lum. Very friendly guy and one heck of a potter. This hand carved foot is beautiful!
Even more fantastic examples can be found at Flyeschool. There is even a PDF guide to the classic vessel shapes and foot ring types – http://flyeschool.com/content/japanese-tea-bowl-feet