Could you do something like this? This is bininah soapstone for the hearth and surround. They are going to build a wood mantle around it

Is your fireplace more for decoration or do you want to use it as a source of heat in the event the electricity goes out? I would make any changes to the fireplace now since it's open.

The stone you have placed on the fireplace looks really nice. It looks as though the trim or baseboard to the floor is already white, so may as well keep it that way with the fireplace.

For the mantle: Are there any architectural salvage stores near you? You may find an interesting piece that would work in that corner space. Sometimes they'll have stone or wood mantels.

Can you see the fireplace from your kitchen? If so, the fireplace should reflect the style or colors of the kitchen. For example, if your counters in the kitchen are marble, do marble around your insert if they’re soapstone, put soapstone around the insert. Or, you could just repeat the color of the cabinets in the mantle. For the hearth, I’d do a stone (same stone you choose for the surround) tile and keep the baseboards. Good luck! I love a good fireplace facelift!

Thanks for the suggestions. the fireplace is visible from the kitchen so I will tie in the same grey tones. hopefully can find a stone tile for the hearth that will work