Cut the top off to be perfectly horizontal and build a sundial on top of it. Plant climbing, flowering vines around the bottom such as morning glory, moon flower, and clematis.
Our favorite is to level off the stump and place a small garden statue (like an angel) or a bird feeder on the stump, then plant agressive vines all around in a large circle. Another is a large cicle of flowers.
Hollow it out (build a fire on the top and let it burn down into the stump) and use it as a planter for annuals. Build a flower bed around it also and plant perennials to complement it.