I like to use more than one border in my quilt... it give more of a "framed" effect. I would go with a narrow/skinny inner border of the lightest or darkest color in the fabric. For the next border use a middle color and make the size to give you a quilt you want. Using two borders will help to balance the overall borders width with the rest of the quilt. It won't look so much like you were just trying to make it bigger.