Thanks everyone for your comments. It's funny, I had in my head that I'd fill in all those details (vegetation, cities) as the players learned about the peninsula, but if you think about it, putting in the mountains doesn't make any more sense than putting in forests and stuff. I agree that staggering the mountains is a great idea, so when I get the chance I'll give that a go! Political borders is something I'd love to do at some point, but I think I'll leave that for a different style of map.