Hi @SacredSlang
JavaScript is used to automatically determine the image width/height, it will depend on the browser window size to calculate the space for the image preview, did you try using different browsers?
Also, I’ve checked your website and I can see you have added this code snippet in (X > Theme Options > JS):
function isa_order_received_text($text,$order){return'<p>Thank you very much! Your order has been received and will be packed up shortly, a receipt has been emailed. A notification will be sent once your order has been completed and shipped. :) </p>';}
add_filter('woocommerce_thankyou_order_received_text','isa_order_received_text',10,2);
However, this is a PHP code snippet not a JS one, so that’s not the correct place to add such a code, PHP code snippets can be added to functions.php file in your child theme directory, check this guide to know more about child themes.
Thanks.