Many people express uncertainty about hanging large wallposters in small, enclosed apartments. Contrary to popular opinion, however, big posters often belong in small rooms. Of course, you don't want to clutter up your apartment with lots of big posters--one should do to serve as a major focal point. You want to hang art that goes with a theme. If you are a huge sports fan, put up posters of your favorite players or hang framed memorabilia. Try not to mix and match--sports posters typically will not ''go'' with animal prints, for example. Along those lines, choose wallposters which harmonize. Don't diversify your wallposter collection to the point that it lacks any sense of center. Discard or store old wallposters that fail to mesh with your general scene.College students and teenagers may want to dress up their rooms with fun or whimsical posters. If you're a professional or a postgraduate student, you may want to avoid hanging up too many whimsical posters, however, for fear of appearing somewhat less mature. If you do want to add levity in an otherwise serious environment, you might try framing the poster or offsetting it to the side somehow, so that its ''jokey'' quality doesn't take over the room.So-called landscape paintings may be appropriate for doctors' offices and small workshops. Home decor designers are also likely to recommend tasteful posters to bring color and creativity to a room's appearance. Finally, you'll want to make sure that your poster frames match up with one another, and that you have hung your wallposters low enough to create an impression of a larger space. Believe it or not, even common posters can appreciate in value over a few years. Preserve your collectible wall art by framing. Don't tape or glue bent edges, or you could devalue your pieces.