Find it, Make it, Love it: DIY Board and Batten-Master Bedroom. This is a great tutorial and would work for adding a picture ledge to an old door or window too. May work in the guest space with a ledge less panel covering the electrical panel.
DIY: How to Build a Faux CofferedCeiling - this post shows how the ceiling is divided into sections and how beams are created using blocks and strips of wood. This is a clever way to add a ton of character for very little money - via Design Dump