You just reminded me of this really great post:
Is Fan Art Illegal?
This is an SDCC seminar by a copyright lawyer who used to work for Paramount Pictures. It's like an hour long but really good. If you don't have the time the main points are summarised in the article/post under the video.
Basically:
I still buy and commission fan art thoughDo you own the character in question?
Yes? Do what you please!
No? You have no legal right to profit from work featuring characters without permission from copyright holder.
No? You have almost no rights to create such works not for a profit, either.the artist alley at botcon was the best!