Pahom,
вариант как я понимаю, что такое фон
<html>
<head>
<title>Программа приветствия</title>
<style type="text/css">
html, body{
height: 100%;
}
body{
background-image: url(https://mdn.github.io/dom-examples/streams/png-transform-stream/png-logo.png);
background-size: cover;
background-repeat: no-repeat;
}
</style>
</head>
<body>
<script type="text/javascript">
addEventListener('load', function(){
var element = document.getElementById('img');
images = ['https://js.pngtree.com/v3/images/home/paradrop.png',
'https://img.pngio.com/instagram-logo-png-images-instagram-logo-clipart-free-download-instagramlogo-png-310_308.jpg',
'https://www.pngarts.com/files/3/Light-PNG-Image-Background.png',
'https://png.pngtree.com/png-clipart/20190929/ourmid/pngtree-creative-irregular-solid-graphic-text-box-png-image_1755152.jpg'],
j = images.length, i = 0,
show = function(){i = ++i % j; element.src = images[i]; setTimeout(show, 1500)};
show();
})
</script>
<img id="img" />
</body>
</html>