I think that for an image a text string can be given that will be read when viewed by an auditory user And that would probably be more clear with the letters spelled out in English than the greek letters So I don t think that is a problem And since the fraternity web page simply says The Official Flag is of royal purple background with the fraternity s Greek initials in the center and a star in the upper right hand corner Both the initials and the star are white Each chapter may place in the upper left hand corner the Greek letter or letters which designate it in the Fraternity one of the users who specializes in graphics could probably create one in a couple of minutes