Why change it? Why not just change the color of the mantle? (Wood) Or for that matter remove the formal mantle and use just a shelf?

it just seems a bit contemporary for the era of the house

I would change the candles to blue ones and you will have the perfect beach pallete - blue, white and tan, sky, surf and sand!

Do you mean change the fire box?

White surround around the fireplace seems like a pure white which is isolating your fireplace and also making it look muddy. I would change the surround to a warm greyed down colour to make it work together. Pick a warm white for your paneling as well.

I was going all sarcastic about gray, but that doesn't help you. Are you near the beach? Collecting beach stones to augment a selected natural stone veneer will bring the beach home and cover over that somewhat lame tile. Using a more textured dark, natural stone will also contrast well with the smooth white paint. It is maybe a more expensive option than olldbobbi's redecorating...but probably less than a total interior repaint.

The tile color is great however, its glossy contemporary shine takes away from the cozy beach look that exudes the room. A less expensive way would be refacing with a painted sandy-colored wood. A more expensive way is a sandy colored coral stone...I once had one in my Florida home and it was the focal point of my room. You may want to add some pale blues and grays such as a few throw pillows nearby.

I really don't see the fireplace being problematic. However I would consider painting the room to give the beachy feel. As well as distinction from the fireplace that is subtle, yet noticeable.