If you have the fabric I would continue the pattern on the sides so it doesn't look cut off too. I would go with a dark rose color the darker pink/rose color of the quilt. It would not take away the view's eye from the beautiful florels. I think a blue would fight with the fabrics.
It's a beautiful quilt and you did a great job. It's basically like a bargello and trip around the world....so I would finish the "pattern" if you can!