Carpets.

If you are going for passive solar retention then I would suggest tile or natural stone. I prefer tile. A good quality porcelain can look just like a real natural stone without the maintenance

I appreciate your rapid response.

I adore a Mediterranean red cement, yet love an abstract mosaic Picasso look. I figured cement won't achieve my goal. I also prefer a porcelain over stone. Will it be difficult to buy/lay in large squares? It's my understanding that larger pieces give the illusion of a larger space.