<div class="container"></div>

body{
  background: #FFFFD4;
}

.container{
  width: 128px;
  height: 128px;
  margin: 0 auto;
  background: url(https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/Creative-Tail-Animal-mouse.svg/128px-Creative-Tail-Animal-mouse.svg.png);
}

/*
A larger herd of elephants is served to anything above 650px
*/
@media screen and (min-width:650px){
  .container{
    background: url(https://upload.wikimedia.org/wikipedia/commons/3/30/Borneoelephants.jpg);
    width:650px;
    height: 650px;
    border-radius: 50%;
  }
}