dhananjaysingh

Using this plugin you can associate one image with each of your category created in wordpress. and you can call that image by using provided function in any template file 
 tejus_dj_getcatimg($catid) 
call this function in any template file it will return url of that image. 
where $catid is category id of that category. 
my facebook profile : https://www.facebook.com/dhananjay.singh2 
my company website: http://tejuscreative.com/

category image

Using this plugin you can add images to categories

stephenbaugh

This plugin gives you the ability to add a category introduction to each post. I have multiple topics I blog about and therefore want to put the post in prespective by sharing the category I added it to. No editing of themes is required to use the plugin and a default layout is setup on install. Play with the html layout until you get exactly what you want. 3 tags are provided to give you access to the category data [categoryID], [categoryTitle] and [categoryDescription] also optionally you can use php if you are an advanced user.
Tags are evaluated first, then php before the results are returned.
For more detailed information and installation information please visit this plugins <a href="http://www.stephenbaugh.com/blog/wordpress-plugins/category-intro-post/" rel="nofollow ugc">home page</a>
The html layout has 3 tags available
<ol>
<li>[categoryID] </li>
<li>[categoryTitle]</li>
<li>[categoryDescription]</li>
</ol>
<h3>Support</h3>
To ask questions, find answers to issues & make requests visit my <a href="http://www.stephenbaugh.com/blog/forums/" rel="nofollow ugc">forums</a>

Tui's Category Intro For Post

This plugin has been written to insert a category introduction to each post, based on its main category and that categories despription.

category image vs Tui's Category Intro For Post