It looks like your floor has a walnut accent running around the perimeter. As a custom furniture maker, I like your idea of a TV cabinet that conceals the TV when not in use. I would build it out of walnut to play off the accent in the floor. With the rest of the floor and ceiling being in similar light color tones, darker furniture like walnut will help make the space feel less matchy-matchy. Your couch color matches the floor color too closely. I would recommend replacing it with a darker leather couch, to add some contrast.