Sajed Ahmed

This plugin is used for add a custom column field to post screen like post title,post category etc.This plugin is create a new column 
named “Featured Image” and the content is the particular post’s feature image which is uploaded by the wp-admin Post page.When this plugin activated you will see the Featured Image box at bottom right side of Add New Post page and also you’ll see the new “Featured Image” 
column on the manage Posts screen.

Wp-ImageColumn

Add featured image Column to the WP Posts Screen

gapgag55

Thumbnail RecentPost is widget for your recent post. The standard widget recent port of wordpress. There is not a thumbnail. if you using this plugin you will have thumbnails recent post.

Wp-ImageColumn vs Thumbnail RecentPost