My first thought was a black border and a white border (to balance all the orange in the top). Not sure what order I would put them in - I would audition them on both sides to see which one frames better. I'm thinking that a black border would stop the eye too much and make an outer border of white seem odd (also, white on the very outside would get dirty fast). So probably an inner border of white and then an outer border of black - both fairly narrow.