It depends what kind of look you are going for but I agree a cleaner look on the fireplace would look nice against the floor which in itself has a ton of color variation.

I’m always a fan of limewash over paint on brick if you are going to go a white/light color. Allows you to keep the natural charm of brick but get the updated feel. Look at Romabio Paints on Instagram for inspiration.

I like the look of your fireplace now! It looks like antique brick. And I like the way it looks with your tile floor. I'd replace the mantle with a chunky hand hewn beam type mantle. Or a mantle with antique corbel supports? Or a mantle made from an antique architectural salvage piece? Leave the brick! It looks great! If you find the brick is too busy with the tile, put down an area rug to take away a bit of the busy-ness. Maybe an area rug with a lot of soft cream colour and not much pattern.

I would wait until you furnish the room to decide. I like the brick as it is, and maybe after a rug and furnishings the variation in the fireplace and Saltillo tiles won't stand out so much. You may have a hard time with the gray paint and Saltillo tiles - typically you would use warm whites or colors with them.

I agree that the brick looks good. It is just that the room is empty.