Shutters, Shades, Blinds -  Plantation shutters accentuate a bay window or an arch window.  Shades soften the sunlight as it comes through the window and gives a warm glow to any room.   Blinds give you the ability to have a direct view of the outside and are typically the least expensive of the three options.

Valances - Purely decorative, a valance helps establish a room's style.  It hangs across the top of a window , adding softness, color, and pattern to the window.