I have created an Android app, and a Discord bot, "Art Prompts". The point of the project is to give artists inspiration via short prompts, such as Draw a vampire standing in front of a mirror, looking for his reflection.
I'm currently in the process of creating Premium categories for the app and bot - categories of prompts the user has to pay to unlock.
Can I create a Fan Art category as one of the premium ones? For example Draw Bill Cipher in the Weirdmageddon. (Gravity Falls), or Draw Mercy bringing Widowmaker back to life. (Overwatch)?
Is there any trouble I could get into by doing this, because of trademarked names, or the copyrighted IPs?
EDIT: The apps offer 6 free categories of prompts (Places, Animals, People, Fantasy, Sci-fi, Horror). The only difference between the prompts in the free categories and the premium categories is the topic (and the price, obviously).
The apps don't show any images inspired by the prompts - only the sentences themselves.