I would definitely move the tree to the top left corner so that your pieced blocks are aligned together on the sides and tops and the 'live' blocks are in the corner. I would also put a frame around the center block either with flying geese or just a nice border. I like your blocks as they are but a sashing would work also. I definitely would use a narrow border and then a wider border picking out colors from your quilt. You did a great job on this quilt, I think it will be a winner.