Just like you pass tags in your WordPress blog posts; you can also tag images using a free WordPress plugin called WP Media Tagger. The plugin is extensively configurable and comes packed with a bunch of features enabling WordPress media tagging and search & media taxonomy etc.
Install and activate WP MediaTagger plugin. After activation visit Dashboard -> Settings -> Media Tagger, sort your images and configure options and the best part is that the plugin is workable with your existing post tags.
Now for displaying Media Tag Cloud you can use its widget, after activation the plugin adds a Media Tag Widget in Dashboard -> Appearance -> Widgets page which you can use in your site’s widget areas. OR you can may use shortcode [mediatagger] for same purpose.
Main Plugin Features:
- Associate tags to medias from the Tag Editor
- List all the medias of your site and associated tags in one central place to ease the tagging process with the Media Explorer
- Associate tags to medias from any post or page by clicking on your media captions
- Provide access to deep media search on any media associated to a list of tags, through a tag cloud, tag form or combined search display
- Select a display mode for your result page : itemized media list, thumbnail gallery, or media captions
- Any combination of search mode and result display style is possible
- Seamless integration in your sidebar thanks to the MediaTagger tagcloud widget, with direct connection to the media tagging database you just built
- The MediaTagger media taxonomy can optionally supersede the default post taxonomy
- Database integrity checkers are provided along with the fixing routines