I presume that this is a wood burning fireplace? If so, it probably does need a large metal flue like the one you have. Only 2 ideas come to mind: "box it in" and replace the windows behind it (so it looks more intentional), or replace the unit with a sealed gas-only until. Most of those units can vent directly out the back (verify the proper model) and don't need a vertical flue like you have.

The easiest solution would be to paint the ceiling darker than the walls so the metal pipe sort of blends in.

I would leave the mantle empty for now (no lamps).

I agree with 2M ..
If you can, look into venting it directly outside. I've seen a lot of houses with the fireplace built out that way.
I'm assuming that the fireplace is against the back wall under the Windows... The picture sort of gives the illusion that the fireplace is floating in the room.

Thanks. Yes the fireplace is back on the wall and not floating in the room. Would you the window mullins wood color or paint white??

I am partial to white trim, but that's just my preference.