Shane Gowland

This plugin adds support for Topic Thumbnails with bbPress. It works by retrieving the first image from each topic and displaying it alongside the topic title on the index page. Thumbnails are sized according to the default ‘thumbnail’ size in your WordPress media settings. The images will also resize appropriately if you’re using a responsive WordPress theme.
This plugin works with GD bbPress Attachments and most other bbPress image management plugins.
If you enable this plugin while bbPress is disabled (or not installed) it will display a warning message.

bbPress Topic Thumbnails

Provides bbPress with support for topic thumbnails.

Robin W

Pascal Casier

Adds an option to the Discussion meta box to use a bbPress topic instead of WordPress comments, and displays that topic beneath the post on your site.
You can let the plugin create a new topic for you in the forum of your choice, or specify an existing topic to attach to the post. 
A topic can be attached to as many posts as you’d like, but only one topic can currently be attached to a post.

Post Comments as bbPress Topics

Great support!

I use it to link my Learndash to bbpress forums so that my students can discuss a lesson, either under it or in a forum topic. Really practical, glad that this plugin exists!

Really practical, glad that this plugin exists!

Replace the comments on your WordPress blog posts with topics from an integrated bbPress install

bbPress Topic Thumbnails vs Post Comments as bbPress Topics