There are two great backyard games that can easily be played using any croquet set.
The first is 9-Wicket, "the game we all played as a child in grand ma's backyard. We will discuss that below.
The second is Golf Croquet, either the configuration shown in the Golf Croquet section under "Education", or you can set it up like a golf course and play hole to hole, under trees and around the bushes, what fun!