I, like a lot of others, see two quilts. The idea of having the tree as a baby quilt now & turning into a wallhanging later is a great idea. I'd echo the tree a few times & do a filller with the rest of the panel. The twister would look good with a SITD. I'd use either an off white or black print backing on both. I'd use one of the fabrics in the main pattern. Beautiful work.