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.

Depends on how you want to style it, but I think this would look lovely and make your room feel nice and cozy.

I have a Jotul F500 fireplace which on the inside right wall is cracked. Can this be fixed please?

Not wanting to build anything just make this fireplace look nicer and not so much of an eye sore... cheap and DIY as it's a temporary house!