I would say anything goes; if you could make an extra dalhia and center it or put it in one corner that would make back art ! Its really whatever you like. My personal preference would be solid or the yellow from the front. I'm a matchy matchy kinda girl. I would like to share with you that I have some of those dalhia blocks ready to be put together from my grandmother..... I was so excited when I saw your post and I checked it out ! Love the yellow sashing ! Inspiration...inspiration ! Enjoy ~ please post pics when completed; are you going to had quilt it ? Maybe some crosshatching ?