I noted while going through the great appendices discs that accompany the LOTR Special Extended Edition that some of the conceptions examined for how Shelob should look were more unusual than the giant spider in the finished film. What went into the decision to make Shelob more restrained in conception than some of the other creatures in the movie, say "The Watcher In The Water" - which was considerably different from a giant octopus? I can't say enough for your work on those films BTW; your design work left me sitting in the theater absolutely slack-jawed with delight.
A lot of the design work for the movies would go through a huge number of variations before being pinned down, and this is really to give Peter the opportunity to explore every possibility, so that he can feel happy that there isnít another even better idea around the corner. But that approved drawing will only really be the starting point for another round of design work, this time focusing on maquettes, and when that has borne fruit, another design process starts with the sculpting of a larger, scannable model. The design process is continued with the creature as a digital model, and is often still being refined as the creature starts to be seen in shots. But to answer your question, there is always a balance to be struck between fantasy and realism. A more fantastic, but less ďspideryĒ creature would probably have been less scary. The modellers and animators achieved the effect they did by studying the things about spiders that made them feel most uncomfortable, and Peter was in there right to the end, pushing her face out of shape so that she would look as demented as she was terrifying. Well, it worked on me anyway. The Watcher? I donít think that Tolkien ever defined what it was, but I didnít ever think of it as a giant squid or octopus. I think that it was just one of the many unknown and nameless horrors that haunt the depths below the Mines of Moria. An opportunity for the Weta designers to go fishing in the depths of their own imaginations.