Here are some images that may help you much...
TheOneRing.net Scrapbook
These are images from a Swedish design magazine about decorating your house in the style of the elves.
I agree with everyone else. For a Rivendell style of room use a lot of flowing fabrics, muted light, candles, light colored woods. From the movie it looked like they used a combination of whitewashed furnature and light wooded furnature. Everything should look muted, and relaxing.