This image actually works both as a beautiful drawing and as a chilling background. It works so well with the tone they were trying to create, for what goes on deep in the woods.
This background is used to establish location quite a lot. The trees in the background appear as anonymous as ever, and the way they fade, the further into the background they go, creates a sense of isolation, the feeling of being lost in the middle of nowhere, and that the further into the woods they go the more mysteries they will find. And on a side-note, I love the little joke with the sign "Mystery Shack" spelling out "Mystery Hack" when the "S" falls off.