I’m not sure what you mean by decorating the fireplace, but I feel lining up the art with the fireplace will work better than in the middle of the chimney breast, as it is now.

It's further than I thought. My concern was the stepped in wall and also the opening to the dining area but as it's further up than I thought the ".entrance" should be fine. You would however be left with an alcove between new and old fire. I wonder what shelves would look like there (I couldn't find an exact pic) or just box it in.. Tadelakt is similar to polished concrete, polished plaster, microcement etc, you could look at any of them just to add a bit of texture/warmth. You could always pay someone to do a CAD design in your room if this is your preferred option? Having said that if you frequently have large parties maybe it's not a great idea to have a fixed structure there? Maybe a tv and fire side by side is a better option? Will see if I can find a pic

I'd remove the fire tools too (they should be on the floor, I think). A plant that will hang down the side (perhaps a Scindapsus or Philodendron) on the part where the tools now are would be enough decoration on the fireplace for me. I would however prefer a wall to wall TV shelf on the TV side and art on that wall. Just something simple. A shelf below it for the technical stuff? A large basket with logs on the left side maybe? See my bad photoshop effort :-)

I honestly don't think it will be a huge deal to have the fireplace to the side (I'm usually very OCD about having things symetrical) if the fire surround is going also that sortof means it won't be such a huge chunky thing and you could tone it down.. of you brought a wood burner you could get one of those long tall ones and then almost turn that corner into the 'cosy' area- I'm afraid I don't have an image of this but my friend has done it and it looks really good you can still have the sofas boardering the room the whole way round but just have the log burner in the corner