Keep in mind there are tons of places that people probably have just never really explored yet.
Way north of Gridania comes to mind, where my friend told me he saw the Goobbues or whatever from the Ul'Dah storyline opening.
There are also Flamesomething Drakes east of Camp Drybone that people have already mentioned.
But if you look around with the map, there are crazy looking places way off in the distance that probably haven't been explored extensively (for good reasons!). The image looks like it might take place around the Limsa area though. Maybe it's a boss mob or something SE is planning on incorporating later.
Edit: Just was running around outside Ul'Dah and someone shouted "snake boss monster appeared!" Tried asking her about it, but didn't get a response. Don't know if that's related, but interesting.
Edited, Oct 3rd 2010 4:12am by ArkWeldwin