dmikam

This simple plugin permits you to upload images to categories, tags and custom taxonomies just like to posts. 
This feature is very useful when you want to show unique image in header tor every category or even some slideshow of images. 
Also you can show a list of categories/subcategories with a little thumbnail am much more.
By the way, this plugin just uses wordpress native functionality – no aditional tables and nothing like that. 
Also it uses wordpress images so all sizes are generated automatically (custom sizes included).

WP Category Images

Simple plugin that permits to images to Categories, Tags and Custom Taxonomies.

Bernhard Riedl

This plugin is a <a href="https://www.bernhard-riedl.com/2010/08/01/tagpages-tags-functionality-for-pages-in-wordpress-30/" rel="nofollow ugc">follow-up</a> to the post which I wrote <a href="https://www.bernhard-riedl.com/2007/10/06/wordpress-23-tagging-posts-and-pages/" rel="nofollow ugc">a few years ago</a>. – The idea was (and still is) to equip pages with <a href="https://en.support.wordpress.com/posts/tags/" rel="nofollow ugc">tags</a> and include their number in a combined posts and pages <a href="https://codex.wordpress.org/Function_Reference/wp_tag_cloud" rel="nofollow ugc">tag-cloud</a>.
TagPages is fully compatible with <a href="https://codex.wordpress.org/Administration_Over_SSL" rel="nofollow ugc">https/SSL/TLS-sites</a> and WordPress multisite network.
Plugin’s website: <a href="https://www.bernhard-riedl.com/projects/" rel="nofollow ugc">https://www.bernhard-riedl.com/projects/</a>
Author’s website: <a href="https://www.bernhard-riedl.com/" rel="nofollow ugc">https://www.bernhard-riedl.com/</a>

WP Category Images vs TagPages