I requested permission to post my renders of "Dragonriders of Pern" to the internet and the response was
"I'm afraid we cannot grant your request because those rights are currently
tied up with Pern's media prospects. Regardless of your commercial
intentions, we just don't have the rights to grant to you. Thank you very
much for asking though."

Then I asked who I could contact that could give permission. Apparently it's a sensitive time right now.

I always try to make an effort to get permission if it's derived from someone else's work. I know they have been trying to get someone to make a movie so this may be part of the problem. I'll try again in about 2 months but I'm not holding my breath. :)