Here are a few ideas for customizing your stockings!
The easiest thing to do is to glue or sew on some decorations. Your local craft store or superstore has lots of cute things in the Christmas section. The snowman on the stocking below is an ornament that was stitched on with sewing thread. You can also sew or glue on felt cutouts. The striped stocking below has little xmas light charms sewn on the rolled edge.
The green stocking (below) has a clay ornament glued to the side, and a bit of feather boa sewn to the top edge. The next stocking (below) has the name applied with duplicate stitch embroidery.