I have also tried to have different template styles with Joomla 3 with no luck.

As a temporary solution I changed the style name in the template file Eg mytemplate/category_item.php to span.catItemImage2 and added the style to the k2css

Not an ideal soltion but works for now until there is another solution

I've been trying to do some template overrides recently in K2, on Joomla 3. The posted video tutorial looks helpful, but the CSS4k2 download is no longer available, and I don't believe it works with Joomla 3 from what I've read. I'm sure this is probably more straight forward than I imagine. Is there more recent documentation available for Joomla 3 / K2 template overrides? Thanks!

@Jim Van Zile

You can still place components/com_k2/css/k2.css to templates/YOUR_TEMPLATE/css/k2.css to override it.