There's no real set of Open Graph types. You can create your own, so there is no limitation. There are some that are built-in to Facebook, like "article", "website", "video", and "movie", but you're not limited to just those.
As for where you can use from JFBConnect, the answer is anywhere. You can create an Open Graph object in the admin area and set a 'type' or other values for all K2 articles (or just a specific category of them). You can add the {SCOpenGraph type=xyz} tag anywhere. If you're using a custom type, use the {SCOpenGraph type=ns:mycustomtype} syntax. The ns will be replaced automatically by your FB app namespace.
I hope that helps,
Alex
Open Graph Overrides
