We got this stone from lowes, it is inexpensive and easy DIY. Lowes will make the cuts for you and we glued it on with heavy duty construction adhesive, no grouting. Took us a couple hours with our borrowed tile saw. They have one with grey instead of the gold and cream that we used that might be perfect and you could keep the floor slate. I would go over the top of the slate if it where me doing the work and not take off the old slate. We applied the stone after the mantle was installed and painted. They also have other styles that you might like. http://www.lowes.com/ProductDisplay?partNumber=354393-93840-20-616&langId=-1&storeId=10151&productId=3477519&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1 http://www.lowes.com/ProductDisplay?partNumber=354383-93840-20-626&langId=-1&storeId=10151&productId=3362742&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

My First suggestion would be NO mirrors below the mantle..that will not be a good addition for this space...such a beautiful space you have with the vaulted ceilings. If possible I would continue the brick on both sides so the fireplace continues all the way it will give it some heft and balance out the room with the vaulted ceiling and beams...if this brick can not be matched I would add brick and paint out all the brick to match....add a big colorful piece of wall..since you have acess to electrical on that wall I would bring it up to both sides above mantle and install wall sconces.

There are window films to help with direct sunlight and the fading of decor. These windows are filmed yet that still lets in a great amount of light if no treatments of some sort. As for the floors, they are the original hardwood, are 21 years old now, and they need a new lease on life or a complete change. We are ready for a change! Kids are grown but we have two dogs, so we are considering wood plank tile.

Please stcked stone is already dated and IMO never really belonged indoors at all If you really want help we need info . What is your style maybe some pics of your interiors where you are , IMO the srched window will drive the rest of the design of the FP.