Country curtains or drapery can be textured with nubs, slubs, and irregularities, or be made of homespun yarns, plaids, brushed denim or duck, boucle, hopsacking, heavily textured batiste, unbleached muslin, coarse oxford cloth, ticking, or tweed - all possible choices for country kitchen curtains and/or other rustic window treatments.
Prints with nature or animal themes may work with your rustic decor theme. Or, lace curtains against a wood background can create a great juxtaposition of cool and crisp against the warmth of wood - elegance against rustic.
Valances can be used with curtains or with shades or blinds to add some definition and texture to your window.