Clan avatars. It takes a lot of effort for very little return. This is not much. Battlefields. Fantastic tech that got press in standard media for gaming But, who uses them? The majority of people visit Clan Wars and the Wilderness when they are looking to fight. Battlefields aren't likely to be asymmetrical, or even strange.
In addition to the fact that aside from the gain in xp, a clan citadel does nothing for you in the game of runescape itself. The clan cape features three stars, and a vexillum includes fireworks. Is this really the end of the story? Apart from clan members, no one ever visits your castle.