Greg - SiteOrigin

The Theme Checklist plugin is an unofficial tool to help developers get their theme ready for the WordPress.org theme directory. Install the plugin, then navigate to Tools > Theme Checklist to start checking.
We’ve compiled a some of the most common theme issues that we see in the theme review queue and put them on our site, <a href="http://themechecklist.org" rel="nofollow ugc">Theme Checklist</a>. This plugin simply loads in all the latest checks and gives you an easy interface to check off the issues as you check them in your own theme. Each issue has a detailed description with examples to help you avoid the them in your own theme.
Checks are dynamically loaded from the <a href="http://themechecklist.org" rel="nofollow ugc">Theme Checklist</a> website to ensure you’re always working with the latest version of the checks. If this fails, the plugin will fall back to the bundled checks in checks.json.

Theme Checklist

The Theme Checklist plugin is an unofficial tool to help developers get their theme ready for the WordPress.org theme directory.

zackdesign

RSS Image Widget fetches images from any RSS/Atom feed that uses enclosures and displays them in a responsive grid with a built-in lightbox. Works as both a classic widget and a Gutenberg block.
Features:
<ul>
<li>Widget + Block — Use in sidebars (classic widget) or anywhere in the block editor</li>
<li>Lightweight — No jQuery, no external CDN. Just a tiny vanilla JS lightbox (~2 KB)</li>
<li>Responsive grid — CSS Grid layout adapts to any container width</li>
<li>Lazy loading — Images use native browser lazy loading</li>
<li>Accessible — Lightbox supports keyboard navigation (Escape to close)</li>
<li>Zero configuration — Just add a feed URL and go</li>
</ul>
Upgrading from v2.x:
The Bootstrap classes (<code>row</code>, <code>col-xs-12</code>) and external Lightbox2 CDN have been replaced with clean semantic HTML, a responsive CSS Grid layout, and a bundled vanilla JS lightbox. If you had custom CSS targeting the old classes, you will need to update it to use the new <code>.rss-image-gallery</code> BEM classes.

RSS Image Widget

Display images from an RSS or Atom feed as a widget or block with a lightweight lightbox gallery.

Theme Checklist vs RSS Image Widget