There is no answer from the specialists
It is the holidays where I am from.
The currently browsing each post functionality, I am not sure, there is not a plugin that I am aware of that can do this for bbPress specifically or for WordPress custom post types. There are user online plugins that display all users online on the site as an alternative to this. You may need to hire a developer to create this currently browsing functionality for you.
– bbPress Advanced Statistics
– WP – useronline
The images by each forum, follow this topic.
https://bbpress.org/forums/topic/add-a-featured-image-to-a-forum/