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Domino Magazine's before & after gallery featuring the addition of this faux mantle really creates the illusion of depth and sparks architectural interest in the space.
I also love this post from Becoming Home and how happy this couple was by creating a faux fireplace in their bedroom. It anchored their floorplan and created ambiance.
Also, check out sites where you can can buy your own faux fireplace for a reasonable price. Like this Heritage White Gel fireplace.