By default WooCommerce doesn’t display category images on the products archive page. Here is a snippet that will allow you to automatically add category images without modifying your theme files. Simply copy and paste the following code in your functions.php file, within your theme folder.
Of course this snippet is the very basic, you can add custom CSS classes, IDs and more, but that’s a pretty good start. Simply keep in mind that WooCommerce doesn’t show category images by default and that’s intended, it’s not a bug. Feel free to r-use that snippet and make it your own, also post a link to your shop page when you customized it! ;-)