Basically, any kind of physical change you can think of, though I doubt you could mess with brain chemistry. SUPPOSEDLY one of my friend's brother's friends has been doing this sorta stuff all his life, and he was able to turn himself into some sort of lizard-man thing. Very iffy, but I dont doubt that it would be possible if someone were powerful enough, or through advanced genetic manipulation. As for growing extra... things, read about mitosis. If its possible to do so through aura workings, then get a big plate of food so you can supply nutrients to your new tail.