Planning a stacked-stone garden wall? A few randomly placed terra-cotta architectural ornaments will add an unexpected hit of color—and character—to the usual expanse of gray. These decorative relief tiles, recovered from old buildings, can be found at salvage yards. As you lay the natural fieldstone, stack up stones around and behind each tile to hold it in place, with its edges flush to the wall’s face. In shade, moss will quickly grow on the tiles, increasing your wall’s looks-like-it’s-been-there-forever appeal.