.layout-transparent {
  background: url('http://www.getmdl.io/assets/demos/transparent.jpg') center / cover;
}
.layout-transparent .mdl-layout__header,
.layout-transparent .mdl-layout__drawer-button {
  /* This background is dark, so we set text to white. Use 87% black instead if
     your background is light. */
  color: white;
}