This image of the Pantocrator has been used in domes and icons from the beginnings of Christianity. Pantocrator means Almighty One, or Most Powerful. But the icon found in St. Catherine's is particularly interesting because it has two faces: serious and not, judgemental and merciful, disapproving and kind, etc. Look at the left and right side.
My favorite interpretation is the one that portrays the image as representing the two natures of Jesus: human and divine. Depending on your perception of God, which would be which. I like to think that the human nature is the judgemental side; and the merciful side is the divine side.
What do you see?