This list includes a range of content that can be noncommercial or commercial, but can be able to make Fair Use of trademarks in either circumstance, as the commercial nature of the follow-on work is not the sole determinor.
This image from an etsy store showcases works that include a trademarked element from the Harry Potter series - namely, the House colors - but use it in a way that has a commercial element, but otherwise meets the criteria for Fair Use of a trademark (as well as of a copyright).
Again, fans make a point about the Harry Potter series by using a trademark from the Harry Potter series - the Weasley Sweaters - as well as the trademarked characters, who are also protected by copyright.
Creative fans usually do not want to create pursuant to licenses, or to make money.
Yes, some fans want to create authorized content or work under a license from the copyright/trademark owner. But most fans want to continue their discussion in artistic and narrative forms, and if they use trademarks in the process, that's ancillary to the story they want to tell or the visual they want to share.
TIP: don't say "I don't own anything" in the disclaimer, or someone may take your creation and sell it on Amazon under the (mistaken) belief that what you've shared is in the public domain. In the US, it usually won't be, because it's complicated to give up copyright in a work. Instead, say something like: This story is based on characters and situations created and owned by [_____________]. No money is being made and no copyright or trademark infringement is intended; I reasonably believe that any use of third party copyrights and/or trademarks is pursuant to Fair Use principles and laws.
Should we have a DMTA - a Digital Millennium Trademark Act - with a safe harbor for sites that go through a process in taking down allegedly infringing works, and putting works back up if the follow-on creator shows why they are not infringing?