Take down your artwork. It's too much of a mishmash and all hung at different levels. I would replace it with big framed prints or canvases. You could go for either sepia, B&W or colourful, but not two of them or all three.
Get a big piece of framed art or a mirror and hang it over the fireplace, vertically, with the bottom of the frame quite close to the top of the fireplace (i.e. no more then 9 inches from fireplace to bottom of picture or mirror). This needs to be a real statement piece if art. A mirror would be best though, as it would make the space appear wider.
Where are all the tall units gone from your previous home? You need them back. Put books in them, or colourful knick knacks. Or both. They could go on the window wall and the fireplace wall. If the units went with the house, consider getting some of your own to put in the room.
Get a rug in a warm colour and maybe an oval shape to break up the rectangularity- red/orange, green/purple.
You need lamps instead of the ceiling light. Consider lampshades in colours other than cream/white.
Get colourful curtains that are longer than the ones currently in place (colour could match one in the new rug). Couch cushions in same or complementary shades.
Big plants in big baskets or structured pots - by the window (get little stands on casters so you won't destroy the floor underneath with moisture).
www.amazon.co.uk/Rollers-Outdoor-Planter-Trolley-Casters/dp/B077TPKLWR?tag=mumsnetforu03-21
If you're able to move the couch in front of the window with the chaise longue part close to the fireplace I would do that, and move the TV to the wall facing the fireplace on the dining room end of the room, with plants and/or another tall unit to the left, then put tall units where the TV is now.