I would paint all the walls. The artwork needs more color behind it. BM Flame 2012-20, or eggplant 1379, and the gray I would consider is Alaskan Husky. The track heads is could be adjusted as the light is hitting the picture inconsistently and creating dark spots.

Love to see you do something else with the fireplace itself as to decor. Great space!

I would install a mini quartzite on that wall and add texture and color.

I like judyg's idea of emphasizing the art wall with the plum or eggplant in the painting. I wouldn't paint the fireplace wall. Instead, I would clear off the raised hearth and add some cushions that reference the painting. Add to that couple of your plants near the window and a candle or two and you've got a nice arrangement and casual seating.

Thank you for all the comments. I like the idea of colour behind the painting. Should clear away all that stuff. Would you know where those seat pillows are from?

Pulling some color from the painting to the firepalce wall would work great! A plum or green above the firplace would tie the room together. Seat pillows on the hearth are a fantastic idea! You might also add an accessory or two to the mantle (a vase, sculpural piece, etc.) to add interest and dimension.

I don't have a source for the cushions above, but similar ones can be found at these places:

http://www.ebay.com/itm/300725619687

https://www.tara-home.com/tarahome_alpha/floor_cushions

And a good selection here on Houzz:

http://www.houzz.com/photos/products/Cotton-Floor-cushions

Colors above for wall above fireplace OR behind art piece :)

I love that painting, the photographs over the fireplace and the room is great. I would do a light grey on three walls and a plum behind the painting. Edit all the small stuff to just a few pieces and a substantial plant. Do you feel like you need window coverings?