These tiles were made by hand carving rubber stamps and pressing them into stoneware clay. They were glaze fired to Cone 10.

Here is a tutorial I wrote about carving rubber stamps:
http://www.limegreennews.com/howcarv.html

And here is another about making ceramic tiles from rubber stamps:
http://www.carolynsstampstore.com/catalog/mosaic_table_top_with_textured_clay_tiles.php