If this was my room, I would paint the brick two shades darker than the walls. In my opinion, the brick fireplace is dated. I you do that, keep in mind that is a maintenance challenge. The vases are ok, but they are too similar. Add some interest to this area. My mother always loved decorating the mantle. She had a lot of different vases, small framed pictures, and small sculptures to work with. She also had a different color theme each time. You don't need to get that elaborate. It depends what your decor goal is, and how much effort and time you want to put into it. I am lazy, so I keep the same decor for years!!! I would pick up the green from your wall art and paint the mantle that color, but that's me. This is your space - decorate it as you see fit.

a few more photos showing the whole room, all walls.

For me, the TV art is too vivid. although it looks like you like colorful pop art, the brick fireplace isn't featured, just the TV art. It doesn't need any thing on the mantle. I would not paint the brick, unless/until you change the floorings, etc.

There are other things in the room I would update, long before I tackle the look of the fireplace mantle. Start by centering the area rug ON the fireplace and arrange furniture so that the fireplace is the focal point of the room.

I would tone down the TV art to something simple and tonal, remove the matching vases.

Fill the wood box with firewood (even if you have to buy pieces just to fill it up.

a tarnished metal ash pot or even a large basket with fire starters (pine cones, etc.)

... my pet peeve is the seam showing on a lamp shade (spin the seam to the wall)

”I would tone down the TV art to something simple and tonal, remove the matching vases.”

I agree, along with Lyn’s other suggestions. For me, fireplaces and mantels look best with simple decor, especially when brick is involved since it can be busy.

I'd do a mortar smear on the brick