I used to believe that you never combined washed and unwashed fabrics, however, a local quilt shop owner says, and I am now a convert, that it really doesn't make a difference...especially if your quilt has smaller pieces of fabric. The smaller the piece of fabric, the less noticeable any shrinkage will be on the overall look. If you use unwashed backing fabric and unwashed batting, you should get the wrinkled look that you (and I) like even if some of the front pieces are pre=washed.