Here is an interesting way to repurpose those old tubes. What you can do is get old used tubes that you have no other use for. Get a block of wood.
Cut a few slits into the tube and cut out the valve stem from a few other tubes. Now insert the stems into the slits of the tube you cut. Glue or tape the valve stems in place. Now you are ready to stretch the tube over the wooden block. Either staple or glue the rubber to the wood and you should be all finished!