This plugin allows to set a featured image for each category. 
Posts without a featured image set will show the category’s featured image instead. 
Featured images usually are placed by the theme in the single post page, in the latest posts page, etc. 
But can also be shown using the shortcode [cfi_featured_image] or the PHP function cfi_featured_image(). To get the featured image URL I added the function cfi_featured_image_url().
Shortcode/PHP function optional arguments:
<ul>
<li>‘size’: ‘thumbnail’, ‘medium’, ‘large’, ‘full’</li>
<li>‘class’: class of the image tag</li>
<li>‘alt’: alternative text of the image tag</li>
<li>‘title’: title of the image tag</li>
<li>‘cat_id’: select a specific category id</li>
</ul>
Shortcode example:
<pre><code>[cfi_featured_image size="large" title="This is a test..." class="my-image" alt="My image"]
</code></pre>
Function example 1:
<pre><code>cfi_featured_image( array( 'size' => 'large', 'title' => 'This is a test...', 'class' => 'my-image', 'alt' => 'My image' ) );
</code></pre>
Function example 2:
<pre><code>cfi_featured_image_url( array( 'size' => 'large' ) );
</code></pre>
Notes:
<ul>
<li>If a post has more than a category with a featured image the first available is loaded</li>
<li>If a category hasn’t a featured image but it has a parent category with a featured image the parent one is loaded</li>
</ul>

Category Featured Images

This plugin does one thing and it does it well.
It's easy to use, too: install, set up the default category images and forget about it.



Does one thing and does it well

Set a featured image for all the posts of a category.

Jesper van Engelen

Adding multiple categories in WordPress can be a real pain. When you want categories for every country in the world, it is a horrible job to fill out and submit the new category form hundreds of times, especially if you’re adding terms that have a hierarchy!
BulkPress makes this process much easier, by providing you with an easy-to-user interface to add categories (and terms of custom taxonomies) and pages/posts (and posts of custom post types) in bulk, giving you the option to specify a hierarchy in the added posts or terms.
BulkPress can spare you hours of your time, just try and find out for yourself!
<h4>More to come…</h4>
BulkPress will be updated with new functionalities very regularly. What to think of the following features coming to your WordPress installations soon…
<ul>
<li>Mass add users</li>
<li>Specify attributes for the pages you’re creating in bulk, such as the page template</li>
<li>Promoting multiple users to a different role in one go</li>
<li>Much, much more…</li>
</ul>
<h4>Feature requests</h4>
If you have any feature requests for this plugin to allow you to mass manage content more easily, just drop the suggestion in the forums!

BulkPress

It does what it says. "It just works". Would be be great if we could add categories or tags to each post but that's fine.

Tested with Wordpress 5.8 and it works like a charm.

FANTASTIC!!

Add posts, pages, categories and custom post types and taxonomy terms in bulk! Managing vast amounts of content made a walk in the park!

Category Featured Images vs BulkPress