I don't have a fence, but like this idea. Find old windows, replace the glass with mirrors and put these on your fence (if you can). The mirrored image of your garden on the fence will make your yard look bigger. It's an easy trick!
Tuffits: Concrete stepping stones which look like pillows! Concrete stepping stones that look like vintage pillows. Get old pillows, lather with petroleum jelly, cover with plaster of paris. once hardened, remove pillow and fill mold with concrete!