I'm sure lots of folks will share great ideas & tools around polls, team-building events, etc. And definitely look into those.
Something else I'll mention is that the facilitator matters a lot. I think of it like "Can this person's personality come through the screen and meet users on the other side?" There's definitely a difference between people with great in-person skills vs. being able to communicate those through the screen. If you can find someone who can project their personality through the screen, that's engaging and captivating. No amount of interactive exercises will compensate for an unengaging facilitator.