I've done 1 cloth shower curtain but not a quilted one. I wouldn't put any batting in. The cotton would absorb moisture and get very heavy.... plus you'd have the mildew thing going on inside the layers. I would make my quilt like any other quilt (no batting) and put my grommits on the one side. But I wouldn't attach the liner to the quilt. That's the way I have my shower curtains here at home. I can wash the outer decorative curtain without a problem. And, if the plastic liner gets ugly, I can replace that without destroying my pretty cloth curtain. Good luck with your project.