I am interested in all of these options. If you are considering exclusive posts, videos, previews, etc., they don't have to be exclusive forever. Backers/Patrons can just get them a week ahead of everyone else. Lots of devs do that. I'd also be interested in designing a monster, item, class, etc., or writing a small story for a player quest. Early alpha access might be an interesting tier, and might help you with feedback.
Hopefully other people can think of additional rewards. Another problem would be publicizing your Patreon (if you went with Patreon). Some of us on this forum would sign up, but I'm not sure how many people that would amount to total. You are popular at QT3, so maybe some of those folks would sign up, or maybe random people on the steam forums who like your games if you made a post on Steam.