Funny you mention terrain generation, as I went a little overboard while adding copper ore last week.... Long story short, 1.3 will have a brand new terrain generation algorithm, which should add some nice variety. There are deserts, savannah, highlands, mountains, grasslands, and forests. More biomes are likely to be added in the future as well. It also produces the occasional island as well.
1.3 will introduce resources that only appear in certain biomes. Copper ore and stone only show in mountains and highlands, while fertile soil only shows in grasslands along rivers. I don't want to make that restriction with mudbrick, since pretty much everything requires it.