The Chat is something I have tried using in the 10 years I have been a member here and my experience was similar to Joachim's and Kaizerwolf's experience.
I am going to try and address your goal of bringing more people to the site.
Arqade seems to have a problem with active users participation. Look at the voter turnout. It was very low for this election. I personally am asking and answering less these days.
We are definitely in the right direction with the Photo contests but a few more ideas couldn't hurt.
One idea IMO of building traction and user engagement is doing what any of the SE sites do best. Quality Q&A content is what attracted me to the site in the first place.
I came in when we had run contests if I remember correctly around ME3 and Skyrim. And it brought a lot of content to the site also and new users like myself. People asking and answering competitively, as gamers are wont to do. So much so that those two game tags have pretty exhaustive question pools.
So we could target up-coming releases and run contests. Open a Meta page where you can track upcoming game releases so people know to set their calendars week to week.
The current contest with Sci Fi is good and all, but to me personally it feels like the games targeted have already exhausted question pools on the site already. What more could you add to that, that hasn't already been asked before and therefore closed as dupe.
There is one more thing that can be done and that is actively marketing the site and content. But that would merit another discussion since there are potentially many ways to do so with varying budgets.