Have a look at this drawing by Tolkien - "Mordor Special Mission Flying Corps" emblem for the Nazgūl:
Emblems
"The Mordor Special Mission Flying Corps Emblem apparently was a badge that applied to Sauron's air-borne troops, probably including the later incarnations of the Nazgūl and, perhaps, any remaining dragons under Sauron's command. The "wings" at the side of the emblem are given a feather-like texture, which might indicate that they were originally real wings. A mystifying scribble, saying "Seen from below", actually hints that the emblem portrays one of Sauron's flying creatures, and the small "horns" indicated between the wings and the body of the creature could then be the feet of someone riding the beast. But it is clear that if so, the portrait must be extremely stylized. On the wings can be seen the image of Sauron's eye, multiplied like the eyes on peacock's wings.
(Reference: 1. Hammond and Scull. J.R.R. Tolkien: Artist and Illustrator. Patterns and Devices )
Cute, isn't it? Bright like a butterfly...
