Jolly,
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title></title>
<style type='text/css'>
#test{
display:none;
}
</style>
<script type='text/javascript'>
window.onload=function(){
var image = document.getElementById("test");
var i = 0, s = ["block","none"],t = [5000,5000]; //2 сек есть картинка, 5 сек нет
function show()
{
image.style.display = s[i];
i ^= 1
i && setTimeout(show,t[i]);
}
setTimeout(show,t[i]);
}
</script>
</head>
<body>
<img id="test" src="https://javascript.ru/forum/images/ca_serenity/misc/logo.gif">
</body>
</html>