There are two things that can change the look of a room without breaking the old bank. One would be paint, and the other would be with decorative pillows. There are pillows for every style, taste, and budget.
I have a pretty good collection myself, and once every so often when the spirit moves me I make a change and I have a brand new look in which ever room I'm working on. A good rule to follow when you are arranging pillows is to always arrange a group of pillows in an odd number amount. Also, don't be afraid to use different patterns. As long as you keep the colors harmonious the effect will be interesting, unexpected, and exciting.
You can find a huge and really fabulous collection of them here. Home Decor from BurkeDecor.com