Maybe some exposed, natural-wood ceiling beams?

Wood moulding around the windows. A faux wall/wallpaper that looks like logs and mortor.

Maybe some nautral logs in each corner and then the faux wood beams? Not sure about the additional weight to the ceiling though...

52mary's suggestion of wallpaper is a nice ,light treatment. If you are going for a more textural space, reclaimed wood boards of varying widths/ sizes could also be applied. Look at simple burlap window treatments hung from branches and rough edge shelving, spindle wood and painted casegoods, and metal storage container accents, in addition to all the usual suspects. Good luck with your project.