I found this piece of driftwood a couple of years ago and it has always been inside (dried to a grey white), but the children kept on pulling it down and whatever mischief they could think of, so I took it out, where it's slowly turning brown and grey.
I liked the contrast against the slate and the gravel.
I love the tones of black and white, the contrast, and the texture. I have bits and pieces of driftwood all over the house -- I can't resist dragging sticks, stones, and shells home.