.hero .hero-media {
   background-image:url(http://s3.amazonaws.com/imagescloud/images/aines/20160401-m.jpg);
}

@media only screen and (min-width: 768px) {
  .hero .hero-media {
    background-image:url(http://s3.amazonaws.com/imagescloud/images/aines/20160401.jpg);
}
}

.is-winter .hero .hero-media {
  background-image:url(http://s3.amazonaws.com/imagescloud/images/aines/20151001-m.jpg);
}

@media only screen and (min-width: 768px) {
  .is-winter .hero .hero-media {
    background-image:url(http://s3.amazonaws.com/imagescloud/images/aines/20151001.jpg);
  }
}