Remove brass screen replace with all black. Do not paint stone.

Place both birds together at one end. Add a taller bigger item at other end. Something in green like in pic. Don't place things on either side of FP, group together and add color from pic. To tie it together.

Put two people below on mantel. Add tall pot in green to hearth. Remove plant to small.

I would paint a pear green. Walls look boring.

The stone is very nice and I wouldn't paint it! I think it's the wall color that doesn't complement the stone is why you feel you need to paint. I would get a simple, updated screen for the fireplace and paint the walls a soft dove gray to complement your stone, floor and art. I really like the simple lines of this pewter FP screen and will update instantly. This screen will also hide the brick back wall you don't like.

I agree with above comments, do not paint it black! That would be too severe. I like the stone color.

Oh please do not paint the stone !!!! I would also consider replacing brass with another color. Possibly black or expresso color! I have found that anything can be painted!! Just another option !