Choose the color of your walls carefully. Colors affect mood, so choose a warm or earthy color for a romantic room, rather than a more impersonal shade. Try playing around with shades of sweet pink and orange, or warm maroons and cool blue, according to your personal tastes.
Once your walls are ready, choose what you want to put on them. While a large vigorous print of a hunting scene might be a good idea for the game room or study, it is hardly romantic. For décor in the heart of your space, choose softer themes, and more artistic renditions, when you choose art for the walls.
Find interesting pieces of statuary, preferably along romantic themes. These look great when placed in wall niches or on small tables in corners, lending a more exotic and romantic look to the room. This of course is subject to the general décor. Greek statues would look laughable, not romantic, in a cool-modern room. So take care to match your artwork to your overall theme.
Strategically placed mirrors are a great idea. They reflect the light in the room, and can make the room look much bigger and deeper than it is. Mirrors also add a lovely dreamlike effect, increasing the personal romantic effect of your room.
Light is an important consideration in setting a romantic mood. While bright lights are great for working in a study or kitchen, romance demands softer lights and more muted effects. Pick softer fluorescents in yellow and pink or choose bulbs with lower wattage. Alternatively choose recessed or spot lighting for a more romantic effect than strip lights or overall bright lighting.
Consider adding a real or faux fireplace to your room, if that is an option. There is nothing more romantic than turning off the lights and having the room illuminated by the dancing flames from a fire.
Place candles around the room, in holders matching your décor. Slim modern candle stands work better for the modern room, while heavy brass candelabra are better for baroque/French/Italian/antique looks.
Burn Incense or place bowls of pot-pourri around your romantic room. This looks lovely, freshens and romanticizes the room, and brings in the fragrances you prefer.