even when using fusable for your applique the appliques are still stitched down so they hold up quite well. I love the idea of window coverings, valances ect. we have patchwork drapes in our bedroom that match our quilt (well one of the quilts anyway) and i am working on a cathedral window project with wow backgrounds and batik windows...i plan to use it for a roman shade in my sewing room.
you can make anything you want with your quilting...be adventurous! but stitch down your appliques if you do not want them to fall off sometime down the road.