Reuse an old tree to make a log pathway in your garden. Good use of "yard" trees and other wood that can't be milled; works much better in climates without termites. Good drainage under the log rounds will make the path last longer.
(link) FOUNTAIN: How to Build a Concrete Fountain ~ Create a stone-lined garden pond, then carve a waterfall out of a block of stone using basic power and hand tools. The technique is simple, even for beginners. This is a STEP BY STEP TUTORIAL GUIDE
Succulent tree trunk - instructions are not in English but the idea is pretty basic. Tree trunk + removal of some wood + soil, water & succulents = awesomeness in your garden! You could even hang this from a patio at eye height.