Use a public domain comic character however you like: make a game, make a comic, create a theme song, whatever. Or, make a character that is Creative Commons licensed or otherwise open-source licensed. Or, make a character each day and outline a comic universe for them (or a TTRPG or whatever)!

Read more about the Golden- and Silver-Age comic characters in the public domain:

https://pdsh.fandom.com/wiki/Public_Domain_Super_Heroes

2 Rules:

• Keep it all PG-13 and below -- that is, no NSFW, offensive content, or excessive gore/violence. And if it gets borderline PG-13, be nice and give a warning.
• Everything needs to use an open license. Note that some of the stories in the Golden and Silver Ages are NOT in the public domain, just certain characters, so updating and modifying the characters is wise.

(Nothing forbids you to use stuff you already worked on.)

Templates from Fabrica de Herois App:

http://fabricadeherois.com.br/#oque

More templates (CC0):