Without knowing how you want to use them on your quilt... would using painted/heat bubbled tyvek work?
You can paint one side of your tyvek with some lumiere paints in several colors, sponging it on for a natural effect. Draw a leaf pattern on the tyvek, including veins, stitch around the tyvek and stitch in the veins, use pinking scissors to cut it out then apply hot iron with thin paper between tyvek and iron, you don't want it to melt on your iron plate. It will bubble and distort and look like a leaf. Sew it on your quilt. Tyvek can be washed.
just a thought
warm quilt hugs, sue in CA