Icon should be square, no more than x pixels, and less than kb in size.
auto join
When autojoin is set to off, new users will not be joined to the room. Existing users can join the room by searching for it in the "find or start chat" dialog. When autojoin is set to on, new users will be joined to the room when they are activated. Existing users who are not in the room will be auto joined to the room after enabling auto join.
moderation
When set to free for all, anyone in the room can edit the name, topic and room icon. Nobody is in control over member ability to speak. When set to moderated, only room moderators can edit details about the room and can mute users if necessary.