Of course it's possible. All you have to do is add the code to swap the link to the item with a link to a larger version of the image.

For that, it's best to have your own set of template overrides for K2. Start here for that: getk2.org/documentation/tutorials/templating-with-k2-and-the-concepts-of-sub-templates

The file you're looking to modify is this: github.com/getk2/k2/blob/master/components/com_k2/templates/default/category_item.php