All neutrals so far - you can add any colors. Depends on the look/feel/style you're going after.

Sophisticated start. You could go with black and white photography, architectural pieces, art pieces- anything you love on the wall. Then, add pillows in the colors of the art work. If you want to stay more monochromatic, think in terms of textural interest, such as a shag area rug, pillows with seam detailing, etc.

It sounds lovely. The ceiling will be more than suitable for a transitional style. I think the wainscoting would also be fine but as I'm cautious I'd be adding after I'd lived there for a while. It does seem more traditional than transitional. On the other side I'd love the bead boarding in the hall.

Sorry for the delay....well I still haven't quite got to the floor yet. I have friends and family advising that black would show up every bit of dust etc and one friend who had a shiny black floor and felt that she was forever mopping, and if the light shone on the floor on the wrong angle you could see where the mop had been. I think this would frustrate me too much especially with young children and a cat so I think a whitewash look could be a good option, or reclaimed battered timber perhaps.......see why I haven't chosen the floor yet. Lol. You could always go a black but a weathered matt reclaimed timber that could look good too. Good luck!