We like the way A Tile Guide describes the paving in this photo as having "grass for grout". Twelve-by-twelve stone tiles are laid out in a grid, with grass in the joints instead of grout...We've seen this often and always like the look, but it's generally with irregularly-shaped, rough stones. The cut stone tile in a strict grid is a cool way to blend the built environment with the natural one. Plus, the ground surface remains pervious when you use grass for "grout", allowing rain water to naturally saturate the earth instead of running off in sheets to the nearest storm drain. See this and more tile ideas at A Tile Guide.