I do my applique shapes with wonderunder fusible on the back and blanket stitch them down. This works on quilting cotton. What are your burp cloth backgrounds? If they are flannel, then a fusible applique should work. If they are terry cloth, it should still work but you will have to be a little more careful ironing them on and stiching the edge. As others have mentioned computer clip art is a good source for images. Our Walmart has big bargain bags of assorted embroidery/applique shapes (with the assorted button bags) in the sewing aisle for about $7? You could check to see if yours carries them and if they could work.