I think the spider should stay due to acceptable breaks from reality and the Rule of Coolâ„¢. None of the Glest mods I've seen so far are built for realism anyway, and most are complete fantasy or only have a vague inspiration from reality, so I think having a giant spider goes right along with that. If somebody wants to make a fairy tale tileset and include unicorns and ogres in it, that's their prerogative, but let's keep them out of the default, shall we? I have no problem including imaginary creatures in default as long as they're pretty close to possible (giant arthropods have existed in the past).