This is one stunning quilt top!
I would add sashing to the left and bottom sides and finish with one wide dark border and dark binding. The quilt has a wonderful diagonal flow and a dark border wouldn't bring that to an abrupt halt. Sort of like the quilt top is the galaxy and it just drifts off into space. (My love of nature and sci-fi just pop up every now and then :D )
Best of all, audition lots of possibilities for borders, take pictures and most likely, one will present itself as THE one.