No, there are several files telling the game how to build them. The tiles are just land masses, their climate and height can turn different.Are the tiles saved as pictures in the files? (Yes I am impatient and instead of generating RNWs again and again it would be easier to just go to the files.
For more info on the file structure you can view the preview from the 20th on Twitch: http://www.twitch.tv/paradoxinteractive/v/26738376