Definitely start with a rug. I don't know what your style is so can't make specific rug suggestion. But, I would take advantage of this neutral palette to choose a rug with a design and colors I love, then add pillows and accessories repeating those colors. Make sure the rug is large enough to be in scale with the sofa. The sofa has pretty hard lines, you might consider a round ottoman out of fabric. Above the sofa you could do artwork in graphic black and white, or color. Don't worry about everything matching. I am a believer that artwork is chosen because you love the piece. It should stand out in the room if you made the decision to invest in something. Check out local colleges the art department has several sales during the year of student art; especially around this time of year. Once you have the rug and ottoman add some chairs for additional seating. Enjoy and have fun.

Absolutely! It will work, couldn't think of a better combo than black and walnut!... as for ideas, depends on type of floor, rug, etc... and photos of the couch and table would assist...

The above idea is good, or you could get some cardboard boxes, cut them to the right dimensions, tape them together and lay them out where the furniture would go (I am better with three dimensions than 2 when it comes to figuring out what works! )

We have just finished building, went with black tapware throughout and black kitchen sink. Only the kitchen tap is both chrome & black as this was the only tap we could get with the hose. We love it.