I would paint the trim the same color as the cabinets

The protruding wall around the fireplace needs to be wallpapered or painted with dense motifs or tiled with stone/brick textured tiles or ply. Re-doing your fireplace will drastically change the look of your living room. See photos below. Consider painting the frames of your doors and sliding doors in the living room and kitchen a dark brown to match the floating shelf over the fireplace. Do not decide what you want to do in poor lighting as you have provided in the photos. Wine is a good color to consider. Also think of darker colors like plum and have different shades on each wall (from the same color family). So maybe think of wine- plum- magenta or wine - oxblood-blood red, etc. whichever suits your taste.

Hi. I love your couch and if light is an issue, I would think about a large mirror because it'll bounce the light around the room (your little starburst one is a bit wasted over there). Mirrors don't have to be expensive - look in charity shops and second hand shops. If you go for a large canvas, make it quite colourful so the boring walls fade away. Again, you don't have to spend a fortune - there are lots of websites with affordable art. A floor lamp would be great and if you get a ceiling light, make sure it isn't so low that it blocks whatever fabulous new item you have hanging behind the couch. I'd see how it looks when you've done this before you paint or also to help choose your paint colour so it goes with mirror/art. Good luck!

Loads of options as you basically have a black canvas. I love a rich teal, or dark turquoise. You could also consider wine or pink, or indeed red, but careful of tones