I always prefer simple mantle decor. Let a large mirror or piece of art be the anchor and add two to four more smaller elements around it. I have been wanting to add some wall sconces on either side of our mirror for a while and I finally pulled the trigger. It really helps to balance the space nicely. I even took a stab at some abstract art (insert gritting teeth emoji :) I am on the hunt for a similar abstract piece to balance the traditional mirror and sconces, but I haven't found it yet, so for now this will work!