Mattia Roccoberton on "[Plugin: Category Featured Images] how to get URL of the image with category id from the database manually"

Hi thamaraiselvam.
I save the categories images id inside a Wordpress option. If you want to see the source code of the plugin it is available to the public:
http://plugins.svn.wordpress.org/category-featured-images/trunk/

My plugin doesn't work with custom taxonomies because it requires 2 actions to work ('edited_category' and 'category_edit_form') and these actions in a custom taxonomy depends on the category slug.