Very cute runner! I like to look at the Quilting Designs on the UrbanElementz website - under Seasonal-Christmas she has 268 designs. I like the doodle trees
Another idea: if you have an embroidery machine you could do some colorful embroidery on the top white section of each stocking? Or even use some decorative stitches?
Whatever you decide, I'm sure it will be great! Be sure to update with a pic, please.