Failed to load images, server responds with 404 not found

What am I missing? Slideshow background function is supposed to use linked images to change the background. It runs locally but not when online.

    // Slideshow Background.
        (function() {

        // Settings.
            var settings = {
                // Images (in the format of 'url': 'alignment').
                    images: {
                        'images/4.jpg': 'center',
                        'images/5.jpg': 'center',
                        'images/3.jpg': 'center'
                    },
                // Delay.
                    delay: 6000
            }; ...

Calling JS in HTML file

<script src="assets/js/ie/html5shiv.js"></script>

Directory screenshot: https://imgur.com/GZYlhqX