There are many things that you can do with an old tree stump. For one, you can turn it into a chair. Set up several chairs beside and in front of it and then put a table in the middle. Or you can us the stump as the table, and surround it with stools lower than it.
Another idea is to turn it into a chess table. Just paint it with a chessboard design and put chess pieces on top. Put two chairs beside the stump. Lastly, you can turn it into a colorful flower planter like what you see here.