The Display Posts Shortcode was written to allow users to easily display listings of posts without knowing PHP or editing template files.
The Views Plugin (part of Toolset) lets you display feeds (and any other post type) in any way you want, without any coding necessary.
This plugin can be used to show thumbnails in the Posts listing screen.
When combined with the Feed to Post add-on, this plugin will allow you to set default thumbnails per category or per tag. You can also set a general default thumbnail to be used when imported items don’t have any images.
This plugin can be used to list posts by category in a post/page using a shortcode.
This plugin makes it easy to automatically display video thumbnails. When you publish a post it will find the first video embedded and retrieve a thumbnail for you. Thumbnails can be saved to your media library and set as a featured image automatically.
From a single field to entire pages, Custom Content Shortcode is a set of commands to display content where you need. The [content] shortcode displays any of the following: posts, pages, custom post types, fields, images, menus, or widget areas.
This plugin allows you to clone a post or page, or edit it as a new draft. Since feed sources are custom post types, this plugin allows you to duplicate feed sources in order to keep the exact same settings. You then just need to change the URL of the feed source.
Using this plugin, or any other lightbox plugin from the WordPress Plugin Repository alongside Feed to Post will allow you to have the imported posts displayed in a lightbox, rather than opening a new page or tab with the post.