Triquetra

Found this triquetra, listed as free to use, on Flickr. The above is not the only version of the triquetra but is most certainly one of the most popular and, as you might imagine, has a long history of religious use. It features on ancient German rune stones as well as being popular among ancient Celtic pagans although not often as a stand alone symbol but rather as featured along with other symbols and text. And, being that it is three pointed, it was also popular with early Christians as representing the Father, Son and The Holy Spirit.  Today it is very popular among neopagans as a triple goddess symbol representing the Maiden, Mother and Crone.