Rocket Chat Customization

Is anyone using Rocket Chat? Have you been able to customize it? I really liked Rocket Chat but had a really hard time customizing it. I liked the old school way of being able to create open Chat rooms. One of the really great features I also liked is that the admin could upload their own stickers. (Admins being able to upload their own stickers should be added to Jitsi). There were also tons of helpful plugins...that unfortunately I was never able to add due to constant errors.