Obviously, your theme should enable featured images for pages or you should use a plugin for this. There are also plugins that allow you to set categories and tags for pages.
Set the post_type attribute. The post_type for pages is "page".
In version 5 of the plugin and up, you can set variables such as post__in and post__not_in (see the shortcode descriptions) to display or exclude specific pages.
[thumbnailgrid post_type="page" post__in="1,2,3"] will display page id's 1, 2 and 3 and no other posts.
[thumbnailgrid post_type="page" post__not_in(1,2,3)] will display all pages except for those with the id's of 1, 2 and 3.