The StoryBanner special Passage’s purpose is to be used to add content to the Left Sidebar, it is not designed to show content that spans the width of the page, that what the PassageHeader special Passage is for.
I must of misunderstood, because earlier you stated…
So, based on the visuals of that image it appears that you are either:
using some technique to suppress the showing of the Left Sidebar.
using the StoryInterface special Passage to create your own custom User Interface.
Which of these are you doing?
If the 1st, then we need to know if you using either:
the UIBar.destroy() or UIBar.hide() function to do that, and if so which function as one reclaims the left blank area of the page that is used to display the side-bar and one doesn’t and that will potentially affect the horizontal centring of Passage content on the page.
Or using custom CSS to “hide” the side-bar, which can also result in the left blank area not being reclaimed if not done correctly. Thus also potentially affecting the horizontal centring of Passage content on the page.
If the 2nd, then we will need to see the HTML contents of your StoryInterface Passage, and the CSS you are using to layout that HTML.
How exactly are you displaying that image in that Passage?
eg. what code are you using, and what CSS are you applying to that code.
What are the native dimensions (width & height) of that image file?