Atlantic Premium Shutters, for example, is a company that offers a selection of coastal theme cutouts, including anchors, sailboats, palm trees and seahorse, plus they can make virtually any type of custom designed cut-out if provided a drawing or template.
Atlantic Premium Shutters are made from composites, and never have to be painted.
Another sources for coastal window shutters is Seaport Shutters.
Castaways Hall offers a great selection of Decorative Coastal Cedar Wood Shutters. Choose from painted or unpainted! These coastal shutters are only decorative.
White Board and Batten PVC Shutters from Island Creek Designs.
Jane Coslick's Decorative Board and Batten Shutters, available in ten different colors. You can see more of Tybee Island designer Jane here where she props a chipped and faded shutter behind the bed!
Another idea for coastal themed shutters is to add decorative hardware. Lovely. These are also board and batten shutters. You can tour this cottage at House Beautiful.