After poking around a bit more, I came up with a solution that works fine:
class Controllers_Images extends Controller_Template
{
public function action_index()
{
//Use Model_Image to find many images
//Create appropriate view
}
public function get_id($id)
{
//Use Model_Image to find specific image
//Create appropriate view
}
}
In routes.php
:
return array(
'images/(:num)'=>'images/id/$1',
//other routing stuff...
);
With this setup, the url "mysite.com/images/1" now appropriately displays the selected image as if "mysite.com/images/id/1" was used instead. Not a huge deal, but it is a nicer interface, which is important!