WP-foro thread prefix
No yet. This is planned in 1.4.x versions.
Please don't use [img] bbCode. wpForo is a HTML content based forum, wpForo doesn't support bbCode. Just put the image URL and it'll be automatically embedded.
In case you want to say thank you !)
We'd really appreciate and be thankful if you leave a good review on plugin page. This is the best way to say thank you to this project and support team.