JSFiddle - React, Tailwind, and code Playground

HTML

<div id="main">
    <img class="bg" src="http://lamininbeauty.co.za/images/massage2.jpg" border="none" />  
</div>

CSS

body{
    margin: 0px;
    padding: 0px;
    overflow: hidden;
}

#main{
    margin: auto;
}

img.bg {
    /* Set rules to fill background */
    max-height: 100%;

    /* Set up proportionate scaling */
    height: auto;

    /* Set up positioning */
    position: fixed;
    
    /* Align horizontally */
    left:0;
    right:0;
    margin:0 auto;    
}