I happen to like asymmetry, but have to agree that the houses just don't work for your beautiful RbyR. I would make a log cabin block to create an inner border, using solids or reads-as-solids of just 2 of the colors in the quilt (one light and one dark) but make it scrappy within the two colors. Then use the license plates and vertical row as outside borders. You can tailor the log cabin blocks to whatever size you need to make the quilt the size you want.