Albert Bertilsson

This plugin gives you an overview of page templates in your site. You get both an overview of all templates and how many pages they have. You also get a detailed view of all the pages using a specific template.
Usage for this can be to identify unused templates and to find pages using specific templates to change them in some way.

Template Usage

Template Usage gives you a simple overview page of all page templates in your site, allowing you to easily find pages using a specific template.

Spencer Brown

This plugin offers you the ability to add custom page template files to your WordPress installation without having to manage 
theme folders or use a ftp client. Simply upload the custom template file you have been working on and it will be registered 
with WordPress as a template option for your pages. This plugin is straight to the point and has a clean user interface using 
W3.CSS.
Plugin menu is located under ‘Appearance’ menu.
Attribution: This post online and code on github by wpexplorer: 
http://www.wpexplorer.com/wordpress-page-templates-plugin/ 
https://github.com/wpexplorer/page-templater

Custom Page Templates Setup

Easily add custom page templates without having to use ftp or keep track of changing themes.

Template Usage vs Custom Page Templates Setup