I think that one is ugly and doesn't fit your space. search, "Ikea bookcase hack' or Ikea hacks for media cabinet or shelving. there are a ton of ideas. or try something like this. its a large open wall space. make it look nice and display books, or artwork, whatever. they even have an Ikea hack using Billy Bookcases that look like built ins. paint the wall a dark color if doing white shelving for a more custom look

I agree with bumblebeez, that you may as well leave the wallpaper until you're ready for a proper redo. if you like how the wallpaper looks for now, then that's what matters! I agree with others who say you should keep the fireplace since it's nice to have and it makes a nice divider for a large room. when you are ready to redo the tile, keep it simple-- so, no to patterned tile, stenciling, etc. you already have lots of patterns in your room when it comes to rugs, upholstrey, etc. if you keep the fireplace simple, it gives more flexibility to choose different room accessories if and when you want to change things up. so my suggestion: a white brick veneer for the vertical surfaces, and some kind of dark tile for the flooring around it. you could have a little fun with the floor tile shapes. choose smaller tiles since it's a smaller area.

I love your roman shades and the panels would be completely unnecessary. It would just add another layer of texture/softness/interest to that wall. If you did do something like that, extending the rod further toward the side walls would balance the windows by taking up some of the extra wallspace on the sides of the window. However, leaving just the shades would be just fine. I just feel you don't need anything else on the walls on the sides of the windows. I could see 2 matching poufs or benches (maybe caramel leather) under each window as a nice filler that would add seating or foot rests.