Fan-created stuff is not necessarily "fine," wishful thinking aside. Even though the studio has often looked the other way, it hardly means that they're relinquishing their intellectual property rights or that they will always tolerate those who use their property.
If you don't actually know about copyright laws, then maybe you shouldn't be spreading this type of FUD.
For me, and the works I've done, I've endeavored to stay strictly within the frameworks of fair use
(as defined by US Copyright Law). For those interested in seeing a case where the boundaries of fan created materials were discussed, I would suggest reading this article and the accompanying decision
While everyone has to decide for themselves what they'll do here, I have set standards that I follow in all of my shared works.
Those of us who don't practice this type of law really have no place trying to pretend that we can hold this stuff over others... or give any legal advice (beyond suggesting reading it for yourself or hiring an attorney). But fortunately the law was designed to protect people on both sides of this issue.