.leaflet-control-zoom-fullscreen.fullscreen-icon {
  background-image: url('../images/fullscreen-icon.png');
  background-size: 26px 26px;
  background-repeat: no-repeat;
  background-position: center;
  width: 30px;
  height: 30px;
  display: block;
}

.leaflet-control-zoom-fullscreen.fullscreen-icon.leaflet-fullscreen-on {
  background-image: url('../images/fullscreen-exit.png');
  background-size: 26px 26px;
  background-repeat: no-repeat;
  background-position: center;
  width: 30px;
  height: 30px;
  display: block;
}