You could put a collection of very tall vases in varying heights. Three would work well and stagger them at different depths.

How about a "library" with shelves and a small, but interesting reading chair and floor lamp. Use a cool ladder to access and maybe add a railing

Well, I think what you have up there now is quite lovely!
;-)
.....sorry, just couldn't resist.

You need to think LARGE!

I'd shop for an oversized "jug" or three - maybe even visit an outdoor garden shops, Pier 1, World Market. Or something woven into extremely tall baskets. Find three things that make a nice grouping. Remember you can turn one on its side.

Pottery Barn used to sell a rattan "tray" that was 42" in diameter - makes a nice backdrop to other pieces. It would be easy to go with a fake plant - but I always hate seeing the spider webs that grow. Altho the jugs etc will also get dusty, etc. it seems to show less when you don't have that set of branches. Tall bamboo in a jug could work.

I would get a carousel horse and place it there ,if you like you can use this spot seasonal ,decorate according to the holidays , think Christmas for example ,a carousel horse and a stack of boxes wrapped in fancy foils and a small decorated Christmas tree or and a poinsettia .

I'd take it out. Let the wall over the fireplace soar.