Red Screen Door Trellis (The red is striking against the white wall. Wood screen doors are still pretty cheap to buy. Wood trim from a big-box hardware store could add detail to the plain screen door. Then all you need is paint!
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!