Good question. I think about this ALOT. As I do want to convince readers to give me money on patreon. BUT, the reason i want money is to make the comic, which takes alot of time, and extra content takes time away from that. sigh... This is a good question for something like patreon. But I do think its important to remember you are giving a comic away for free, you do not need to make more content on top of that for free, you are making content already. just use that. My GUESS is that readers would rather have a new page, than some wordy backstory thing. (maybe im wrong)
but patreon, or ko-fi, or whatever. yeah. Currently I make NSFW pics on patreon for xtra content. but i realized... I am competing with alot of very good artists doing exclusively that, so i think that's dumb. What I should focus on is what I have to offer. Which is a comic, and characters from my comic. So current plan is short B/W mini comics, and bonus sections of the main comic only accessible to patrons. The trick will be, they cannot be important to the story, just silly character moments, and nsfw stuff. And they have to be easy to make... =/
Oh and early access of course... which sadly is only one week ahead. wish it was more.
But I think a good trick is make your bonus content something your already making, like process vids, or high res images, or phone backgrounds of certain pages. Id like to do that stuff eventually.
TLDR: Making the comic is my main focus, and any bonus content I make is to try and convince people to give me money. 