Speaking of which....
http://www.girlgamersuk.com/wp-content/upl...otorcycle-1.jpg
http://walyou.com/wp-content/uploads/2009/...r-motorbike.jpg
http://www.girlgamersuk.com/wp-content/upl...otorcycle-3.jpg
....I'm not sure. I think the Alien one retains more of Giger's original design - the Predator one doesn't look like a motorbike built out of a Predator, but a motorbike with some Predator pieces attached. Mind you, it's a distinctive alternative to the traditional sheep skull. Plus, less chance of gruesome impalement if you have merely human reflexes.
What would look awesome would be if someone in an Alien costume were to ride the Alien bike, it'd look like two Aliens on top.... of each other......
OK, scratch that. It would look like Alien business time Do Xenomorphs even have sex? Presumably the queen's eggs are fertilised somehow... I wonder if that means that all the, for want of a better term, worker Aliens are male?