You mean for you to change the ones that are already there? Or you mean for the game to change how it generates them in the first place?
For 1: You can change them up however you like, provided they still meet the requirements for a valid "house" as defined by the game (see my sig for details.)
For 2: No, there is no way to change how they generate. Your options are to turn generated structures either "on" or "off" before initial world creation, or I'm sure there are plenty of mods out there that will change how existing structures are generated or add completely new ones to the Minecraft experience.