This plugin will help you add a image ( thumbnail ) to Taxonomy like Category, Tag, Custom Taxonomy and display image via Widget, or function name ‘get_taxonomy_image($term_id)’ return URL image.
* Note: I do not add any CSS to Your theme header, and of course Image will have full size as you upload, so if you want to have a small thumbnail, you can add CSS or just upload a small image, if you want to display a banner for one category, you can upload a big picture or banner !
* This plugin include a nice Taxonomy Widget in Admin > Apearance > Widget, please check out !
* This plugin Using plugin Taxonomy Metadata (Michael Yoshitaka Erlewine) !
How to Use ?
First, you need to install this plugin successfully from admin
Then, please go to Setting > Taxonomy Image to active which taxonomy you wish to add image, Tag, Category or Custom taxonomy
And, after that, in edit tag/category screen will have a form to add image/thumbnail/banner
Finnal, Add this code
to category.php in your theme, please place it before H1 tag or anywhere you like, you will see big banner or thumbnail as you uploaded before.