The Category Image Plugin allow you to add image with category.

The WP Multiple Taxonomy Images Plugin allows you to add multiple images to a term. It supports category, tags and custom taxonomies.

Add an image to a category or taxonomy. Display a category image using either a template tag or shortcode.

Have featured and cover images for tags, categories and custom taxonomies

Jam Taxonomy Image will help you have a nicer Category/Tag/Custom Post type Page with banner, and have a nice and powerful Taxonomy Widget