If you are using a template, the HTML output for the photo galleries lives under assets > js > scripts.js. You can play around with it, but it’s a little finicky.
If you are wanting a completely custom photo gallery, I’d recommend using Content Blocks, but placing the outer wrapper for the gallery directly inside your layout file with the content block v65 tag.
When you are setting up the Content Block Template inside WineDirect, only set it up for a single slide. You can then create as many slides as you’d like, by simply adding new Content Blocks that use that specific template.
If you are wanting many custom galleries, this gets a little harder to manage, but it works well for a featured gallery.