Purchase a wall unit cover and slip it over the face of the wall unit. These covers are made specifically for air conditioners and come in a range of sizes and colors for both horizontal and vertical units. Made from vinyl or similar materials, the covers also keep drafts away, leading to a warmer room in the winter. Decorate the wall unit cover or leave it plain.
Install a curtain rod over the wall unit. Hang curtains on the rod that are long enough to extend over the air conditioner. Make the curtains the same height and size as ones on the windows in the room to make the illusion that a window lies beneath instead of a wall unit. Open the curtains when in use.
Place a folding screen, like a Japanese shoji screen, in front of the wall unit. Folding screens have hinges so you can adjust them based on your preferences. Make your own using door hinges, screws and lightweight wood.
Build a cabinet that covers the wall section around the air conditioning unit, if you own the home. Use wood that matches the existing room decor so it blends in with the surroundings. Make sure the doors open completely so the wall unit is easily accessed when needed.