Thinking about my lounge and friend's lounges that I find cosy;
Lighting- not bold and overhead but some softer lamps. I also have those horrible twigs everyone hates 
Soft furnishing- rugs if wooden floors and nice tactile cushions. I always put a cushion on my lap as a habit to cover my tummy!
Not tooooo tidy. Clean, but not like a showroom otherwise I don't feel I can snuggle into the sofa. Maybe a couple of magazines around.
Candles, for lighting and scent.
Most of my friends have cream or soft grey living rooms. I think most colour schemes can be made to feel warm and inviting. One has grey walls and sofas but with yellows and teals in cushions, blankets (ooh yes blanket are nice and cosy) and vases. Another has a more beachy look with cream sofas, and lots of wood but again candles and cushions make it feel homely as do lovely photo frames. I have yellowy cream walls with a big rug of warm colours and brown sofas.
Another friend has lime green walls, new black fabric and leather sofas, seventies inherited furniture and no photos or anything personal. I really don't feel relaxed in there.
Above all, a cat or a lap dog labrador, makes the room!