I was at the craft store yesterday, picking up a few things, and ran across a sheet of white poster board with a subtle, square-gridded pattern to it, which I think was in half inch squares.
The pattern is on the slick side of the material, and is fairly subtle, so it looks like it might be a great alternative material for flooring in buildings and spaceships, etc., etc..
I even thought of using it for a staging area at an airport/spaceport, outside, but I don't know how the slick poster board will react to attempts to grungy it up, with thinned paints, and/or water colors. My guess is probably not well, since it is just coated paper.
However, if you desire the nice, pristine look, of a freshly polished floor, in a modern structure, or spaceship, it should be just the ticket.
A bit expensive, at $2.49 per sheet, but when compared with styrene plastic sheeting, it's a bargain. It's standard poster board size, so perhaps, 18" x 30", or so?
There's also a black option too, but the grid on it is rather difficult to see, in my opinion. Might be better from certain angles, and/or in better lighting, but I didn't examine it too closely to be sure. Good for Imperial vessels under the command of the Emperor, or Darth Vader, I suspect.
I saw it in Joann Fabrics, but imagine other craft stores may carry it too.