Cut the trunks into chunks and use them for pedestals. If you place a bowl garden filled with cascading plants atop each they will be highly decorative. Cut the chunks at varying sizes and line them up to define an informal wall or place them around your garden for decor. They will look great accenting the edge of a staircase, wall or doorway.
Slice the trunk crosswise to create pavers. You can then create paths, patios or outdoor flooring with them.
Make furniture out of your tree(s). Use a large chunk of tree trunk as a rustic stool. Make it about 18" tall so it is comfortable for sitting. Or place three tree stumps together and set a flat slab of wood on top for natural table. A really thick trunk cut at 4' - 7' in length can be set on its side as a woodsy bench. These simplistic benches look great around a fire pit or under a shady tree.
Use pieces of tree trunks and large branches to create informal retaining walls, pathway edgings or simply to place around a pool area to create a woodland feel.
If you are artistic, you can carve your tree trunk into something sculptural for an interesting focal point.
And if you still have wood left over, chop it up for firewood. It will be a cozy way to enjoy for a winter fire. You could even pop popcorn or roast marshmallows. If you have a fire pit, you can enjoy the fire outdoors.
These are only some ways to make good use out of a fallen tree. See how many other ideas you can come up with!