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.
Baseboard is topped with a piece of cap molding, which is small and bends easily to conform to variations in the wall.Installing Baseboards - How to Install Baseboard Molding - Carpentry, Woodworking, Finish & Trim.
27 Easy Remodeling Ideas That Will Completely Transform Your Home (On a budget!) Add faux thick baseboard with this simple trick! -- 27 Easy Remodeling Projects That Will Completely Transform Your Home