For those wondering, the four winged characters surrounding Christ are the Holy Evangelists, referred by their symbols of man (St. Matthew), lion (St. Mark) ox (St. Luke) and eagle (St. John). Often all four have wings.
The "ο ων" that PaperTiger was quizzed upon makes its appearance, as it does always, on the nimbus of Our Lord. It is translated as "the being" or "the existence" and is a reference to the divinity of Christ by reminding us that "through Him all things were made".
Oh my heavens! What a byzantine and greco-centric concept!