I like David's comments above and think that you should select a simple large (12x24") tile for your fireplace, light or dark.

You have a great opportunity here. I do not recommend placing a tv over a fireplace. Yes, we see it often, but it is not practical for two reasons: 1, the tv has to be placed too high and 2, it is hard on the eyes to be looking at the fireplace light and the tv What I would do is to remove the plaster and re-expose the brick. You could paint it an interesting color or resurface it. Then, I would add a unique mantle.If you have the funds, ideally the threshold should be removed (more contemporary) or resurfaced (more traditional style) The wood store could be a book shelf or display shelf. In the right corner, I would place a comfortable reading chair. The TV I would place on a different wall. Without seeing the entire room, I am not sure where.

Well, for lack of a better idea, since you find it a drafty little space. I'm assuming the draft comes in on the right? Most of the necessities in the area are located of the left side; i.e. vent, thermostat, light switch etc. What I would do I think is caulk up the drafty spots, maybe even add sized poster board wrapped in batting I covered in a gorgeous fuscia with diagonal grosgrain ribbons every which way covered with a heavy velvet to be attached to the area above & below the window. (Of course remove the drapes that are hanging in there). This for the purpose of using it as a pin-it board for notes. Attach a table height board covered in felt to carry across the full width of the little room. Leaving just enough space for a comfortable little antique desk chair. Paint the back wall a bright cobalt blue, paint the ceiling a silvery pearlescent white. Find a way to attach a clip-on task lamp. And stretch a heavy duty enough wire across the top of the opening and complete it with a heavy doubled velvet drape with a drooping valance. Place a swag with fringe & jewels on it to be closed when not in use. Voila intrigue is yours!

Is that a window in center above the hearth? Is rock just a facade? Looks like you have a mixture of furniture styles. Windows look more of the modern style while drapes are traditional. I would say pick one style and go with that. From the windows I'd be leaning modern/ contemporary. If the rock is just stuck on wall take it off. Replace with horizontal wood planks stained same as your door casings. No mantle. If that is a window I would either have a stained glass insert made (again using modern lines) or do a faux stain glass painting treatment to add some visual interest.