Try a mural that speaks to your country theme. Hire a professional or try your own hand at painting a cowboy riding through a hilly terrain, several cowboys with a herd of cattle, a farmer in the field, an expanse of prairie at sunset or a group of square dancers. Or just use country-inspired color schemes: red, white and blue; shades of brown to represent the desert or blue-and-white or red-and-white stripes to imitate gingham.
Keep the country theme in mind when selecting your table, chairs and other pieces for the dining room. Look for wooden pieces. Consider using a rustic bench instead of chairs. If you use chairs, re-cover the seat cushions with leather and suede. Tuck a rocking chair into a corner. And you don't have to buy new. Purchase secondhand furniture or repurpose pieces you already have, using sandpaper or crackle paint to give them a rough, weathered look.
Use country accents here and there to play up your theme. Replace that run-of-the-mill light fixture or ceiling fan with a chandelier that works well in a country room. Tie a kerchief onto the backs of chairs. For your curtains, use chambray, burlap or gingham. Hang a wagon wheel, a wreath of branches or a framed country-themed painting on the wall. Or, be a bit more whimsical and hang a framed old-fashioned "WANTED" poster, an enlarged cover from your favorite country music album or poster from your favorite western.
You can really go country with the dining room table itself. For your tablecloth and napkins, use any of the aforementioned textiles, or look online or in sewing supply stores for material with patterns such as cowboys, saddles spurs. For your centerpiece, try using a bonnet or cowboy hat, a coil of rope, a set of horseshoes or branding irons. Use alone or in a grouping. Or use a living centerpiece: a potted cactus or Mason jar full of freshly picked wildflowers.