My sister used to work for Hearth and Home. They supplied a lot of fireplaces and mantels for the TV show Extreme Makeover. Here is their site and the link to some mantels but there may be more links as there are several affiliated manufacturers. May get an idea from these examples.
http://www.hearthnhome.com/index.asp
http://content.hearthnhome.com/downloads/brochures/fsf_mantels_brochure.pdf