before deciding on colours it would be a good idea to consider the best use for such a lovely room, how big is it, are there any doors, where to? will the pool table stay? will you keep the old or another heater? how often will you have overnight guests? would a sofa bed be enough? what do you want to have in a study? will the room need to be more for your own use or visitors? would this room make a better everyday room for yourself and use an alternate room for guests and study?

oklouise has identified some good points to consider.

I think this room could be treated in two possible ways.

Painting the walls and beams white and go for a scandinavian cabin in the woods vibe. if you don't use the fire it could make a head board as due to the windows there isn't a lot of good space for a bed. accessorise with blues and greys - and a whitewashed timber desk. A collection of vintage glass vessels would look good on the mantle piece and a vintage mirror above the fireplace.

Alternately you could continue with what the room is already suggesting as an american style country lodge. You could introduce an aged tan leather sofa or chairs. Introduce a rug and woollen tartan cushions. You may not need to paint the walls as the wood look would work. The windows can be kept stained in a warm wood tone.

Linen or linen look curtains would work well in either scenario.

You could search these styles further in Houzz and consider the style of the rest of your home.

All the best