Someday when we own a home of our own something on my "must have" list is a fireplace with a fabulous mantel. The possibilities are endless! This awesome article from Elle Decor has some great tips. My favorite was from Celerie Kemble:
“A mantel is a central focal point of a room and an easy place to make small changes that help keep a room from feeling stagnant,” says New York designer Celerie Kemble. “Break the symmetry and create visual interest by selecting a collection from a wardrobe of objects: two pretty planters, a pair of candlesticks, a clock, and decorative boxes. You can dress and re-dress your mantel to fit the season using different pieces from your wardrobe.”
You should definitely check out the rest of the gallery, they've got some great ideas!