I see a lot of artists use it as a glorified tip jar, which is my general idea for now. But in the future, I'd love to use it to help fund various projects I have in mind. Basically I'm poor and I'd love to make art my fulltime job, so I'm starting small and thinking about having this as a side-thing.
A monthly patreon raffle or monthly free doodles might be a thing, as well as opportunities for discounts for high-level patreons, but I don't plan on doing full, finished pieces for patrons every month. I don't have the time or resources.