My ingredients list for a good room is a very short one: bright, cheery and simple. One of the easiest ways to achieve this is to keep your main furniture pieces (couch, etc.) quite simple and inject interest with your accessories and accent pieces (art, rugs, etc.).
The room above is simple, but beautiful, and it’s brightness is aided a great deal by that lovely window. If you want to up the brightness-factor in your home, use lots of white/light tones in your room. This is particularly nice because when you add in great features like the Alexander Calder print or the striped rug, they stand out all the more.