I like to find "vintage" embroidered blocks and "save" them. My usual method is to get them all the same size, then sash them with 30's reproduction fabrics to the desirable size. (Either all the same or a mix of colors) I would not add any machine embroidery. To me, that would take away from the original stitching.
Another possibility would be alternating the embroidered blocks with same size fabric blocks (one fabric, or mixed colors in pinwheels or 9-patch designs.) If you want eyes, you could do French knots. I have even sewn on little bitty doll-clothes black buttons for butterfly eyes. Of course, the buttons would go on AFTER the quilting. Have fun!