People are doing fan maps and I haven't heard of any problems. Lord of the Rings is a big time target for fan fiction, some of it really good too. I think if the work is done without any intent to make money you should be fine. There is even Star Trek fan made movies and a couple of series out there and they have no been bothered by the current owners of Star Trek. As long as you work doesn't make any money and if you do copyright your material; do it under Public Domain, so no one can make money selling it.