What should I do with our fireplace?

you could remove the existing mantle and replace it with one that goes the whole width of the fireplace surround and is more in scale with the wall. a material like rundle rock or slate will provide some contrast to all the wood and go with the rustic look of the wall. a larger mirror or framed art will also be more in scale. i might add a slate hearth in front or, you could face the lower third of the wall with slate to break up the expanse of the wood.