|I've read that it's possible to prune forsythias in an espalier fashion, but can't find any pictures showing this.|
|My neighbor has espaliered a forsythia against his chainlink fence. It looks spectacular from winter bloom through autumn leaf drop. You can espalier your forsythia by pinching the terminal bud at the top of the central leader. (Or if it's taller than you want it to be when it branches out, just cut the main stem back to that height.) The result will be two stems growing from the central stem. Train each of these to grow sideways. As new growth appears, select the twigs that will best approximate thedesign you like and rub out, or snip off, the rest. Forsythia's are vigorous growers so you shouldn't have much trouble if you prune the wrong things out. Just wait a while and new buds will appear. I just checked my pruning references and I didn't find an illustration, either, so I'm not sure where to direct you for a visual guide. Perhaps a local nursery or botanic garden can show you with a living example. Enjoy!
Good luck with your new project!