Gareth

This WordPress plugin displays a mini preview window on the edit post or edit page screen.
Mini Preview sits in the Page or Post tab when you are editing a page or post in WordPress.
Buttons above the preview window provide for Refresh, various display sizes, and preview in new tab.
The preview window is a fully functional, interactive mini browser showing exactly what the page will look like, except in miniature.

Mini Preview

Displays a mini preview when a page or post is being edited.

blueimp

<a href="http://blueimp.github.io/Gallery/" rel="nofollow ugc">blueimp Gallery</a> is a touch-enabled, responsive and customizable image and video gallery, carousel and lightbox, optimized for both mobile and desktop web browsers. 
It features swipe, mouse and keyboard navigation, transition effects, slideshow functionality, fullscreen support and on-demand content loading and can be extended to display additional content types. 
This is the official WordPress plugin for the Gallery lightbox functionality. 
By default it automatically adds lightbox functionality to image links ending with gif, jpg, jpeg and png extensions. The plugin provides an options page to disable the automatic feature and to restrict the list of media types. It is also possible to add lightbox functionality for a link manually.

blueimp lightbox

Official blueimp Gallery lightbox for Wordpress.

Mini Preview vs blueimp lightbox