Well I finished my cushion several weeks ago now but totally forgot I needed to post it here!
I did paint a back side to the cushion but when I set the paints with my iron, I missed a section! And it washed out
I wasn't that enamoured with it anyway, so instead I just used plain white cotton drill for the back. I also underlined the silk front with the same cotton drill. I also purchased some white corded piping to use around the edges, but once I got it home and put it against the silk, it was much too "white" (my silk is "natural white" or just a shade lighter than ivory). So, that got left out too, and the result is a much simpler cushion than I originally planned. It also needs a smaller cushion insert so that you don't lose so much of the border.
Anyway, here's my entry into the House Beautiful Contest;