Planking on walls is trending. Accomplish the look with random plank, grooved paneling. www.designthespace.com has laminated/prefinished paneling you can use, or paintable birch paneling to accomplish this look.
Call it Shabby Chic, Rustic Luxe or just Weathered, this plywood paneling with a cedar laminate is just one of many options!(http://www.designthespace.com/plywood-paneling/weathered-cedar-plywood-paneling/)
Think about what your space will be used for. Will the sunroom be used for coffee dates, as a place for kids to play, or as a room for relaxation? Before redecorating, make sure the style of the room correlates with how it will be used daily.