Need Help with Custom Terrain

So my friend is looking for a completly custom terrain world. I've been searching for hours and found nothing but parts of custom terrain. not the whole map. An example of what we would like is this http://gyazo.com/867609ca4cb47e25284d7be522780045 . Im not surw where to find something like that. But anyone who does please reply or if you know how to make THE WHOLE MAP just like that with smooth hills but with grass, please contact me.