Copyright in avatar

I’m developing an online comunity where users can use standards and user defined (hosted in another server) avatars. The comunity will be free for everyone, but I’m planning to charge users for some special options (something like a bigger photo limit, etc) and for sure I’ll use Ads.

The standard avatar set is a list of avatars that is hosted by the site. In this list, I’ve put some avatars from motion pictures like Lord of the Rings and Harry Potter. Can I use this kind of avatar in my site? I know that there are copyrigths in this images but use an image as avatar is a copyright infrigment? If so, does magazines pay royalities to movie studios to publish pictures of the movies?

Sorry for my english.