<img class="bg" src="1920-1080.png"></img>
<img class="bg" src="1080-1920.png"></img>
body, html {
height: 100%;
margin: 0;
overflow-y: hidden;
}
.bg {
height: 100%;
size: cover;
background-position: center;
background-repeat: no-repeat;
background-size: cover;
}