I just saw this thread. What a pretty garden!
The idea of a vine on a trellis is great.
What size shrub are you wanting? Is this area sun, part shade or mostly shade? When you said that it was a wet area, I thought about some of the smaller clethras--like Sixteen Candles and Hummingbird. They would bloom white and have a wonderful fragrance in July/August. I don't know if they're deer resistant though.
