Hang floor-to-ceiling curtains instead of short curtains, blinds or shutters. This will make the windows look taller. Another trick, if you have the time and you're handy, is to fashion a wood panel with molding to go under each window. Paint the panels the same color as the trim around the windows. Karl Sponholtz, a finalist on HGTV's "Design Star," did this in a bedroom makeover to add verticality to the space.
Put tall plants or trees next to the windows. You can use either live greenery or quality silk. Choose trees or plants that fit your decor. For example, if you have a lot of vibrant colors, use silk orange trees, and if you have dark wood or more subdued colors, use silk olive trees.
Use vertical blinds or shutters instead of horizontal ones. Vertical blinds and shutters will make the windows look longer, because your eye will go up and down instead of across the windows.
Place low pieces of furniture like a low bench or ottoman beneath the windows. Low pieces will draw the eye downward, making the windows feel longer than they really are. For even more length, use an ottoman or other piece of furniture with a vertical stripe.
Paint the walls a light color to make the space feel more open than it really is. This will also make your windows seem larger. If you have mostly modern furniture, bright white works well, and if you have antiques or a more eclectic style, light sand and cream are best.