Relating images to taxonomy terms is a common problem I’ve run into when building WordPress sites. To do it completely and effectively it requires the use of multiple hooks, and a non-trivial amount of logic.
Widget Wrangler is a full-featured widget management system for Wordpress. Using Wordpress’s native WYSIWYG, create your widget content exactly as you want it to appear without having to know HTML or CSS.
This plugin provides a user interface for creating WordPress queries (WP_Query), and determining how they will appear. Each query is available as a WordPress widget and a shortcode for easy implementation.