How can I decorate my small bedroom with big furniture's?

It will always look overcrowded no matter what you do. What color are the walls? You need to get them pained in a light color and that will help make the room look bigger. The best solution is to get rid of your furniture on ebay or craigslist and buy new furniture. There are many furniture sites online and you may want to consider modern furniture which are usually a bit more sleek and smaller. Try http://www.leather-furniture-outlet.com/