Do you want them to be visible for the recipient or just for identification while sewing? For sewing I would just write inside the seam allowance. For the recipient I might see if I could find some ready made embroidery details that could be stitched to pieces after the top is together. If you had an embroidery machine you could do them yourself. If not I would look at Michaels for little bows, ribbon rose buds or kiss embroideries. You might even be able to look in the bead department for little hearts etc. to sew on.