I put it on the arm mostly to hide the cloning I had to do on the arm (I had to elongate his arm a bit to accomadate the horns and the width of the pic) and the other part is that i just didnt think of it.
but i'll fib and say that woulda made his head too busy.
I coulda told my art teacher back in the day that it creates an eye catching flow around the image
but the truth is i just didnt think it.