Line and Telegram both let users upload their own sticker sets. And I am a professional cartoonist who thinks nothing of spending her spare time drawing a bunch of goofy drawings of one of her characters. Really I kinda had to; all my pro cartoonist friends have them too, and I felt naked talking to them without a set!

http://egypt.urnash.com/blog/tag/stickers/ has an older version of the set I did for myself. Still haven't posted the set I did for my boyfriend.

I'm looking forwards to being able to dump these into Apple's sticker market. Passive income off of something I did for my own use, woohoo!

(There's also a thriving trade in custom stickers: gimme a couple hundred bucks and I'll crank out a set of goofy, expressive drawings of a cartoon character you like to be on the Internet.)