If you look at demo.getk2.org/categories for example, you'll notice that the images in a category are clickable by default and pointing to each K2 item. If you can't click on your images, it probably means you have K2 template overrides where the link ( element) wrapping the images is removed/stripped. Compare your K2 override for category_item.php inside /templates/YOUR_TEMPLATE/html/com_k2/ (or in a subfolder) with the source override in /components/com_k2/templates/default/category_item.php.

You're welcome :)

Great :)