Wallpaper the room with paper that contains vertical stripes. That works! (Just like vertical striped clothes make someone look taller and slimmer) Horizontal stripes will make the ceiling look lower. So stay away from chair rails, horizontal wallpaper borders, etc. Also, paint the ceiling white.
Otherwise, If you do not wish to paper:
Paint the room white, or a very light color, with the ceiling either the same light color or again white.
These will help some with the appearance, but remember, if you are bumping your head on the ceilings, it won't really raise them.