JSFiddle - React, Tailwind, and code Playground
by zur4ik
HTML
<body id="homepage">
</body>
JavaScript
//get random number from 1 to 4 and assign '.jpg' - or other format you need
var randomImage = "..\/images\/bg\/" + Math.floor((Math.random()*4)+1) + '.jpg';
//get body by ID
var homePageBody = document.getElementById('homepage');
//asign random image to body
homePageBody.style.backgroundImage=randomImage;