For me, that quilt is plenty big enough as it is. I don't use quilts as bedspreads but rather to snuggle under on the couch or to throw over the top of the bed as an extra covering/blanket on a cold night. If they are too big then they are too heavy and cumbersome for me to handle.
I'm with others in a plain border to stop the business and either bind it in the same plain color or make a scrappy binding of all different materials that would coordinate with the quilt. The way I use quilts I always make the border and binding with fabric that is not going to show the dirt easily since that is a heavy wear point.