This seems like a perfect shelf and cabinet layout based on our spacing. Could work nicely if face of fireplace were raw or white brick. Crown molding look? (not sure what to call fireplace surround) may be too formal but generally like.
Tutorial on the Lettered Cottage."First, we bulked up our mantel by attaching wider wood to it. We used a piece of plain pine lumber (that we distressed and stained dark walnut), to create a “slipcover” on top of our existing mantel"