Painting just one wall a bold color is a great way to incorporate a dramatic color in a way that isn't going to be overwhelming. Try painting the ceiling and ceiling medallion white, then use a bold color on just one wall. This will be enough to change the feel of the room, but it won't make you feel closed in.
You can get inspiration for living room colors from home decor magazines and even watching home design shows on TV. When you are ready to order your ceiling medallions be sure to shop around for the best price. The prices can vary and you want to make sure you are getting a fair deal on your medallion. The medallions work well in other rooms as well and will add architectural detail to any room.