To me, Big borders look funny when a quilt is laying flat, or is on a design wall, but very good when it is on the bed as a drop. To test the big border, fold your material so that you have the 12 drop and pin to keep it on the top. I would do this while you are in the bedroom. Back up and look at it. How do you like the big border? Take a picture to get a better perspective of how it actually looks. May quilts and bedspreads are made with a pieced or appliqued top, that rests only on the top of the bed, then solid borders below it. There's no right or wrong....just however you like it.
Your quilt turned out really pretty. I love the colors.