ArcVieh

You can select images from media Library in the Widgets backend that will be shown on your Page. You can enter a size for the images.
The thumb-images will be linked to the full-sized-image. 
Requieres PHP 5!

Media Images Widget

Requieres PHP 5! You can select images from media Library in the Widgets backend that will be shown on your Page.

Martin von Berg

Extend the REST-API to work with WordPress Media-Library. Organize images in Folders. Add and Update images including Metadata and Posts using the images. Access with Authorization only. 
This plugin extends the REST-API of WordPress to directly access the Media-Library for Images. It is intended to be used together with a Lightroom Plugin or as a stand-alone interface for headless WordPress. The new REST-API endpoints (functions) allow to add additional metadata to images, update existing metadata or update images completely without changing the WordPress-ID. Images may be added to the standard directory hierarchy of wordpress or to an additional folder which allows better organization and searching for images. 
NEW FUNCTION : See 3.2

Media Library Extension

Extend the REST-API to work with Wordpress Media-Library. Organize images in Folders. Add and Update images including Metadata and Posts using the ima …

Media Images Widget vs Media Library Extension