Indoor furniture can be used outside, weather permitting. Statues can be crafted from driftwood, stacked stones can make shapes between plants. Large rocks and thicker tree branches make excellent garden edging.
Edmonton Freecycle can be a goldmine for additions to the garden, including plants, organic fertilizers, furniture and topsoil.
Regardless what size your space is, consider splitting it up into different zones or outdoor rooms that have different functions or seating.