lucia.intelisano

If post doesn’t have a set featured image, 
WP Autoset Featured Image Plus check if text contains an image. If yes, set this as featured image, 
if not, you can set any external url image. Otherwise, leave field empty. 
Easy and fast!
Features include:

WP Autoset Featured Image Plus

Check for an image inside text editor or use external images from anywhere as the featured image of your pages and posts.

goresponsive

This widget shows you latest posts featured images in a tiled fashion. It is responsive. You can select the category name you want to display images from. Try it out, it is cool.
Demo: http://onion.goresponsive.in/
documentation
http://goresponsive.in/news-in-pictures-widget/

Go News In Pictures

Plugin for viewing best news photos, news pictures online

WP Autoset Featured Image Plus vs Go News In Pictures