Oh, don't just leave it, it's GORGEOUS!!
I have an idea for you. How about you make a thin border (maybe white?) then you make a stripey border with white and blue on the section with the blue, white and red on the section with the red, and so on? Then another border, maybe with solid cornerstones with each of the four colors? Surely that would be big enough for a wallhanging.
Did that even make sense? Makes sense in my head anyways.