Not sure if this would be more part of Kurento but I can see the need in my business to add a watermark/logo to the stream which is embedded in the video. Does this exist? And is this difficult to do?
Take a look to filters:
https://docs.openvidu.io/en/2.14.0/advanced-features/filters/
You can use gdkpixbufoverlay filter to add an image.
Take into count this will increment CPU usage in the server.
Awesome will take a look