For the most part, the venues we have for large gatherings and parties today are all given the same names that they used for rooms of the same purpose in the renaissance era of Europe. So, just look up those names.
The generic name is "party venue." Although, that is more or less just the proper and less wordy way to say "room you have a party in." So, if you are having a party in a ball room, then the ball room becomes the "party venue." As for the particular terms that are used for they typical types of rooms used as party venues, you can easily just run a web search for "rooms typically used as party venues" in order to get your answer.
kinda weird how the seats are positioned
why do they face the door?
There is a reason for this. Until relatively recently, everyone was always on edge with the idea that someone might be entering the room to cause trouble and threaten someone. So, it was a standard thing that seating would be arranged such that people could have a view of a door. This is not just in high society, you could even see this in places like old western saloons.
In old western saloons, they actually would not place any chairs at a table arranged such that the person sitting in it would have their back to the door. Everyone would avoid sitting in a chair with it's back to the door anyway, so they would simply not bother placing chairs like that since it's a waste of space and resources. Also, the bar itself was always perpendicular to the door. No bar would be straight across the tavern from the door, otherwise nobody would want to sit at the bar stools and have their back to the door.
At the other end of society, in high society, the seat of honor is always the chair that is farthest from the door and also has a good view of all entrances. If we are to consider a drawing room like you are using here, having the seating such that everyone can see the door would be a good and considerate way to make all your guests comfortable since the drawing room is typically a place to entertain guests.
