I agree with the purple rug ideas, but maybe something with a pattern? I like the mirrors idea too, especially if you want to keep it modern. But if you go for art- I wouldn't bother trying to hard to match it to the room- go for something you love. If it has a bit of purple or green or grey in it fine, but don't pick something just because it matches- I think it screams inpersonal.

I would go with a pale grey/beige colour. Something like a Farrow and Ball Dimity or Clunch would look lovely. I think you'll find it hard to match wallpaper so would stick with flat paint. I would then introduce a more definite accent colour and perhaps a new brighter rug. Oranges and mustard yellows would look nice with the sofa. Hope this helps

Out of all the rugs (even though I like the first one in pattern) I think the second one will be good as it will lift the floor but still have a neutral pattern so you can change colours in accessories when you want to. Rugs are expensive so unless you are set on a specific colour theme (like the blue rug or the yellow geometric one) then the second option - or similar, will be easier to move around and take with you. Similarly, something else in a multicoloured tone or with a heavier neutral colour pattern would also work. Down to your colour preferences really?

Remember to look at the aspect of the room, before going for a strong teal colour. It’s extraordinary how different the colours look, depending on whether the room faces north, south, east, or west. And don’t forget nighttime with electric lighting. Also, if your sofa is a deep teal, you could choose a much paler aqua/greeny blue, for your feature walls, and the other walls maybe an even paler shade than those, if your room is light. On the other hand, if the room is a bit gloomy, you could use a contrasting and complementary colour for the feature walls, such as a deep gold, a warm peach, or apricot, or even a warm soft pink (similar, maybe, to F&B’s Setting Plaster or Pink Ground). Depends upon what colours you actually like, as you have to live with it. Teal is basically a blue green, so if not using teal and its paler tones for walls, look for colours that are warm, on the opposite side of the colour wheel.