I agree, no fake fireplace. But you can still do a brick feature wall with a vaulted ceiling and beams and don't need to have a fireplace to pull off a cozy, rustic look. Here are a few examples I found that I think achieve the look and feel without a fireplace. A beautiful brick wall with solid wood mantel and a piece of carefully selected artwork with good lighting can certainly crate a wow factor without the fireplace. Not sure about the curtain here, but love the brick and beams as an example. This one uses the beans vertically and the brick on the ceiling (if the fireplace was out of budget i'm sure this would be too) but at least you can see the options to play with and then scale them to your taste/budget. I love how this one has a great open concept but uses the beams/island to create separation between kitchen/ (and I'm assuming) family room.

You can just add some styrofoam blocks behind a large piece of art (one that fills the niche) to move the art piece forward a bit, so it doesn't look like it's in a hole. You could stick them to the wall and hang the picture from hooks in the top of the niche instead of from the back.

Think about furniture placement. You may not want to put the fireplace centered in the middle of the wall, as it appears your furniture won't be able to be centered in front of it. That bump with the 4' opening is for a door, I assume? Where does the door lead? You will need to leave that whole area along the stairs/living room wall open for a walkway (leaving 42-48" open along the wall would be ideal, IMO) to walk through the living room to the door. If you center the fireplace on the wall, the furniture facing it will need to be off center to account for the walkway. The window and door bump outs are going to be awkward to furnish/decorate around, I'm afraid. It looks like the fireplace wall is just under 17', but after accounting for leaving open space for the walkway, that gives you just under 13' wide of space to work with for arranging furniture in the 10' area (the length of wall with the 3 windows) in front of the fireplace. Or are you planning to put your couch/es in the area where the room widens (the second trio of bump out windows)? If so, how are you going to use the ~13x10' area in front of the fireplace?

The table won’t work, different stain or not. Stick to something more simple, like a clear glass table or even a leather ottoman. You have a lot of grain in your floors. Are you planning on an area rug? You’ll need some color in this room if you’re doing a gray sectional.