Note:
In order to the feature "Use user avatar when thread has no thumbnail" to working properly, please rebuild thread thumbnails by visit AdminCP -> Tools -> Rebuild caches -> "Rebuild thread thumbnails" (check the box "Rebuild threads already have thumbnail") and rebuild.
Add the possibility to set maximum image dimensions for custom-uploaded thumbnails.
Add the possibility to set whether a thread is "video-thread" (Auto-detect by default). If a thread is set to be video-thread, its thumbnail will have an additional play icon.