Cut a 38x36cm rectangle out of an old curtain. The upper edge of the curtain will be used as decoration. Fold the fabric in half right sides together, sew on the machine with a 0.5 seam allowance and then finish the edge of the seam with an overcast stitch. Turn the bags right side out. Cut the desired image from the napkins and separate the layers so that you are only left with one layer.
Place a piece of plastic bag inside the sewn bag to prevent the glue from soaking through. Apply glue to the place where the picture will be (preferably with your finger), lay the napkin on it, apply glue again. Work carefully to prevent the napkin from tearing and let dry for 24 hours.