Apropos of nothing, a thread of panel ideas I would actually go and watch:

The Last 20 Years: Fantasy in the 21st Century
The Last 20 Years: Science Fiction in the 21st Century
Influences Beyond the Literary Canon: RPGs, Video Games, Cartoons

A New Decade of Classics: What books from 2010 - 2020 will we still be talking about in 2100?
An Even Newer Hope: The Next Generation of Star Wars
Beyond the Wardrobe: Modern Children's SFF
Male Power Fantasy: Can We Stop Now?

The Golden Age of Cartoons is Right Now
Fantasy Weapon Smack Down
How to Train Your Spaceship: The tradition of the Living Ship
The Golden Age of Horror Films is Right Now
Modern Folk Horror: Michael Sheen's Excellent Beard in Apostle

Star Trek Discovery: A New Vision of the Far Future
Muscles or eMotions: The Male Characters Who Actually Make Us Thirsty
A Working Class Hero: When We've Had Enough of Kings and Queens
Akira, Cowboy Bebop, Farscape, Mass Effect -What are the new keystones of Science Fiction?

And it should go without saying, the real key to putting together an interesting panel is populating it with a variety of people (regardless of the subject) - diverse genders, ages, backgrounds, ethnicities, sexualities.

Another random thought: moderator is a skilled position, pls don't dump it on someone randomly 5 minutes before the panel. It takes prep, confidence & the ability to herd cats (which is why I never do it). Value your moderator!