i dont think its possible, you'll need to make the art in 1000 ways for characters and or stuff. The easiest way i can think of doing this is by doing what Cryptokitties did "cryptocollectible": https://www.cryptokitties.co/
This still means you have to make the art but at least you dont have to do the full body, you can just add swords, hats, body, mouth, etc to the program. The art gets random which is what you want and players get something. On itch.io it doesn't actually support crypto yet but you can do 1 of 2 things, first you make a website to give players a random booster pack or two, a software to give boosters.