This theme lightly modifies the default 'Copenhagen' theme, mainly to hide comments.
There's a feature request open to permit this functionality without editing the theme, but in my estimation, it's unlikely that it will be implemented: https://support.zendesk.com/hc/en-us/community/posts/207523518-Add-Ability-to-Globally-Turn-Off-Article-Comments?page=1#community_comment_360001714348.
I'm not updating the version defined in the manifest when I make changes - I suggest we use that to track changes in the original 'Copenhagen' theme.
For reference, the BG image (in .hero) is 300px in height across all breakpoints, and is set to background-size: cover;, shrinking to the centre.
The image credit is defined in the bottom of style.css.
Either use the Zendesk ZAT CLI (Previewing theme changes locally), or:
git archive --format zip --output ~/Downloads/newatlas-copenhagen.zip master- https://newatlas.zendesk.com/theming/workbench > Import
You'll need to activate the new theme and delete the old when doing a manual upload.