In short, that is all determined by Spotlight. It should be the same as if you did a Spotlight search of "Kind is Picture". It boils down to the Spotlight importers that you have installed.
If you want to see the "Kind" (or any other metadata) for a specific file, you can use the 'mdls' command in Terminal. There may be a GUI for this somewhere though I don't know what it would be off the top of my head. If anyone knows of any, post it here.