I was recently researching the principle of Temperance (no, not abstinence or some such silly thing), or Balance between two opposing forces or states os being. I was trying to find a symbol for it, and while the Yin - Yang symbol is a good visialisation of this balance, I think it is also overused. I did find however the ancient (celtic?) Arwen symbol, with three stars and three rays of light coming off them. These rays symbolize the male and female on the outer sides and the centre ray is the balance between them.
This is the Balance, or Arwen symbol, as I feel it, I hope I could do such a wonderful thing justice.