I think your tiles need to be larger. Choose an interesting, but simple pattern similar to the one below. I also like the idea of something that is from the region you live. Without seeing your space it is hard to know. You say a stone fireplace, what kind of stone? You want the tiles to go, but to make the fireplace stand out do not go too matchy. Mixing concrete with the tiles can create interest, too.

Hi there Nick, looking at your photos you look like a modern hamptons family which is lovely, do you live in a warm climate. I did like the photo you posted of the open plan living and think that you are on the right track with interior colours I have marked out how I would like the first floor, I have moved the kitchen to the end wall to line up with BBQ outdoor kitchen, plumbing for this would have easy access via the garage below. The white tiles look lovely and hard wearing for the entrance foyer and Rumpus room, the stairs in timber due to the amount of traffic even continuing in up stairs foyer kitchen dining living, Carpet in bedrooms and downstairs theater. Kitchen in white but possibly Shaker style white doors these are very popular. Using existing sliding exterior doors if possible from kitchen.Dining to verandah, I think this ceiling would be best kept white to help reflect light back indoors, the tiles appear to be in good order but you might consider changing these along with new upstairs flooring Some where for a laundry shute would be handy, actually a Dumb Waiter so you could move the laundry with ease both up and down! The roof painted a soft colour, grey/white or off white, the verandah railing could be the same colour or you could do glass. The builder had a very different style of house to what I think you are wanting. Your photo

just had a look at your existing plans for the second storey.. 1/ I'd make it all open plan .. First I'd move your bed 4 downstairs into the theatre room..reason ? bathroom is existing down there..you can turn it into a master suite..bathroom..study as retreat. which then leave you all that room ..bed 4 ..kitchen ..meals..lounge..foyer to just be one huge living area.. from that living area you can pop in a stacker door/bi folds to lead to your screen verandah. Personally I'd get rid of the screens and open it right up with banisters so you can have fresh air flowing in. You can do the same with the front as well to make it one huge area without much changes.

Sliding doors allow for more robust insect/security screens