ummm...I would think of adding rows of pieced blocks using the left over fabrics on both the top and bottom with a strip of the border fabric between the center and the rows and then repeating the border? May be some flying geese or half square triangles.? I would do these rows both on the top and the bottom and leave the side borders until the end so everything is framed? You could also do the additional pieced borders by using the arch's pieces used i the body of the quilt.