Here is a Houzz article on how to decorate fireplace mantels, you might find it helpful. The piece you have now seems to be too tall for the wall shape and space. I would consider an art piece that is horizontal in shape. Keep the hearth decor minimal because your side table appears to be close. Are the items there just to test or ? Adding more room photos would help judge your style.
Are the walls two different colours?

Oops, here is the link.
https://www.houzz.com/magazine/how-to-decorate-your-fireplace-mantel-stsetivw-vs~70969880

I know you’re asking for ways to balance the frame above the mantel, but I think the whole backdrop would show it off better if it were painted in the pale green you have on the wall to the right. The current color, especially with the white mantel, just doesn’t set off the frame in the best way. The next step I’d take would be to paint the bricks white, but I know that’s not everyone’s favorite idea!

I'm not keen on generic objects as a focal point--art would be better--but if you're wedded to the wreath thingy...do an object on one side that's about 1/3 the height, object on the other side that's 2/3 the height. Keep the entire vignette well within the bounds of the mantel.