It looks to me that on the one side of the fireplace you actually have a narrow mantle on the side with no mantle I would paint the brick and just hand a great big piece of art on the brick with no mantle. The side with the mantle I would not paint as the brick is such a small part of that wall.

I just found this on houzz: I would put a bench like this to the left side.

Classic Leather Bench 2 Seat Black · More Info

In this photo, they added a custom steel surround with a shallow mantle. You could do that the width of the hearth.

Langley-Hawthorne Residence · More Info

All great ideas! Here it is with the paneling removed. I believe I'm going to drywall it up where the panels were and run wires for a tv wall mount and perhaps do a shelving unit on the right side. And once all is said and done I could decide to paint or add a steel mantle.

Bookshelves on the left and the wall to right will be removed

Bookshelf, mantle, wall removed Slow progress, but moving forward!

Hi,

To give the room and fireplace a more modern feel you could tile the brick in a horizontal pattern. There are so many fabulous tiles to chose from to blend with any decor. You could also add a long mantel above the width of the fireplace for interest.

Not stacked stone. Your brick will be fine if you either stain it or paint it. I agree that the variegated look is dated.
That is a for-real chimney! Do you live in a climate where the fireplace is useful for heat in the room? You could consider an insert.