Overall
This game is built by our writing together, and a core component of that is being able to add your own works into the official documentation.
There are ofcourse proper procedures for doing so, as all of the documentation exists server side, and has to be manually added by myself, but here you will find all the information you need to get started submitting your own writing and art to the game!
General Guidlines
In general, to submit anything, it should be relevant to the game or game world (an item used by one trainer or a fakemon unique to one NPC is unlikely to appear as an overall entry, unless, for example, that NPC is important enough that many players are likely to encounter it.)
If you're ever unsure about whether something matters or is pertinent, never hesitate to ask! I'm always happy to help and guide you in the right direction.
Rewards
Any artwork or writing that is created for the game itself can be submitted for levels as if it where normal game writing or artwork, setting the participants to your own characters, 2 per submission.