How much light does the room get? I had a navy blue room once and it didn't seem cold at all. I think light charcoal or slate blue can seem very warm& cozy if they are dark enough, and then if you have gold picture frames against it, that warms it up, too. I think lighter blues and grays can seem cold, but not so much with darker shades.

I have a large area rug in my family room that is a frisee texture in a kind of nutty color that we've been really happy with. I can take a picture and post it when I get home. It doesn't show dirt and has worn very well. Even if your furniture color kind of blended into it, maybe you could use some strong colors in pillows to break it up. One word of advice I have received before is that it is easier to pick paint after you have the rug than it is to find a rug after the room is painted!