Hello @Stigan,
Thanks for writing to us.
Add this code in theme option’s CSS to add background image at the background of the menu
.x-navbar.x-navbar-fixed-left {
background-image: url(image url here);
background-position: top;
background-size: cover;
background-repeat: no-repeat;
background-color: transparent;
}
Please change the background-image URL as per your design.
Here is a documentation.
The purpose of providing the custom CSS to show you how to add CSS code to your site. Writing custom CSS is outside the scope of our theme support. If you need more customization, you need to learn CSS and learn how to use the browser’s element inspector.
Hope it helps you.
Thanks