Branches on cakes must be tricky, because I've seen a ton of cakes that have branches that look like snakes or large ropes, or worse, on them.
If you're going to do branches or vines, look at some photos of real ones first. Don't just start piping a snake of brown icing on the cake. Look at CakeWrecks.com if you want to see how that turns out.
When those have set up, carefully remove them and turn them over.
You could either leave them alone or add small flowers or berries to them. To put some glittery "snow" on them you can sprinkle some sanding sugar on the chocolate before it sets up. I left these naked because they were for the gorgeous cemetary cake...So cheerful!