画像の背景を市松模様にするCSS

ichimatsu.css

@namespace url(http://www.w3.org/1999/xhtml);
@-moz-document url-prefix(data:image/), 
               regexp(".*\.(jpe?g|png|gif|bmp|svg|JPE?G|PNG|GIF|BMP|SVG)([?#].*)?$") {
  body {
    background-image: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAAAAABWESUoAAAAHUlEQVQ4y2P4gQYeoAGGUQUjSgG6ALqGUQUjSgEAdjWwLh+tpFgAAAAASUVORK5CYII=") !important;
  }

  body > img[src][alt] {
    box-shadow: 0px 0px 2px 1px navy;
  }

}