I think using different versions of the same fabric is fine. No one is going to notice because they will be seeing different designs. And even if you should happen to "duplicate" a square, as long as they are widely scattered in the quilt, so the eye does not bring them together when scanning the quilt, believe me, they won't notice. And anyway, it's your quilt. As far as I know, the "Quilt Police" have not issued any hard and fast rules on this one!"