Welcome to the Free WordPress Theme Search Engine. I created a Google Custom Search Engine to automatically perform a Google image search for free WordPress themes. It tends to work quite well, as the majority of the results you see in your search will be thumbnails for free WordPress themes on your chosen topic.
To use it, just provide a search term for the kind of theme you want for your WordPress blog. Clicking the thumbnails will take you to the page with the theme you saw in the thumbnail. For example, if your blog is all about sports cars, try searching for sports cars. Most of the search results you see will be thumbnails of sports car WordPress themes.
The search engine page can also accept parameters, if you want to share the results with others. For example, if you want to show your photographer friend some free photography WordPress themes, just link to http://geeklad.com/free-wordpress-theme-search-engine?q=photography.