How to add Image behind navigation bar

Site URL: https://www.nauticalchartwallpaper.com/

How do I add an image behind my navigation bar, I've tried adding the CSS script  into the custom script spot but it doesn't work. Any help would be appreciated. 

The image you show is very different from the URL you provide.

Can we see the site from the image you show?

On another note. Can I just say the concept of map wall paper is fantastic! I really like some of the pics on the website!

Hey, thanks for the reply,

How would I go about showing you the site from the image without actually publishing it. It is something that is a WIP and I don't quite want to publish it yet. Glad you like the idea! We enjoy doing it!

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How would I go about showing you the site from the image without actually publishing it.

Following is the typical blurb I post. If you want to be more selective in who can see your site, you could direct message me with the password.

Please post the URL for a page on your site where we can see your issue.

If your site is not public please set up a site-wide password, if you've not already done so.

Post the password here.

Adding a site-wide password does not allow anyone to alter your site. It only allows those with the password to see your site. Please read the documentation at the link provided to understand how it works.

Please read the documentation at the link provided on how to share a link to your site to understand how it works. A link to the backend of the your site won’t work for us, i.e. a url that contains /config/.

We can then take a look at your issue.