JSFiddle - React, Tailwind, and code Playground

CSS

.corpo {
  background-size: cover;
  background-repeat: no-repeat;
  transition: all 2s ease;
 }

JavaScript

imagens = [ 'loremflickr.com/1920/960/brazil,rio',  'loremflickr.com/1920/960/dog', 'loremflickr.com/1920/960/paris' ]
  var i = 0;  
  elBody = document.getElementsByTagName("body")[0]; 
  elBody.classList.add('corpo'); 
	  setInterval( function() { 
	    elBody.style.backgroundImage = 'url(https://' + imagens[i] + ')';	    
          if ( i < 2 ) {
           i = i + 1;
         }else{
	         i=0;
         }
      }, 4000);