I would not try someone who's income depends on making sales. High gloss floor tiles especially for bathrooms are not ideal since they lack grip once they get wet or when the bathroom is moist after a shower.

I believe the reason the tiles work well with the cabinetry is because the tile is lite in color and flat, its not rustic unlike most terracotta. The expensive cabinets work fine with the floors because of the smooth finish. The floor here is the focal point of this room. The Interior Designer or whoever did this room, did a very nice job, keeping it very simple.

those tiles from the 1800s are encaustic... the color goes all the way through. ceramic tiles are red in the middle and have just a relatively thin layer of color and glaze. porcelain tiles do have a color matched center (look at the edges to tell) but i'm not certain that all of the pattern goes through. at least it would wear off and turn the main color, not red.

I cant imagine that tiles on concrete will be any colder than concrete alone. But the choice of colour may make a difference to the heat absorption qualities; dark tiles will absorb heat better than light coloured ones.