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.

FolioVision

This is a fix of Top Level Category plugin for WordPress 3.1. and further versions. It’s purpose is to provide the same behavior as the original plugin, but in new WordPress versions.
The Top Level Categories plugin allows you to remove the prefix before the URL to your category page. For example, instead of http://foliovision.com/category/work, you can use http://foliovision.com/work for the address of “work” category. WordPress doesn’t allow you to have a blank prefix for categories (they insert <code>category/</code> before the name), this plugin works around that restriction.
This plugin works also if you have a permalink structure like %postname% or %category%/%postname% — this wasn’t possible in the original version. However, this feature might not work properly for child categories at this point. Test carefully!
<a href="http://foliovision.com/support/fv-top-level-categories/" rel="nofollow ugc">Support</a>
<h3>Known Issues / Bugs</h3>
<ol>
<li>Issue with paging and feed URLs when using <code>%postname</code> or <code>%category%/%postname%</code> permalink structure should be fixed.</li>
</ol>
<h3>Uninstall</h3>
<ol>
<li>Deactivate the plugin</li>
<li>That’s it! 🙂</li>
</ol>

FV Top Level Categories

This is a fix of Top Level Categories plugin for Wordpress 3.1. and above.

Category Featured Images vs FV Top Level Categories