Well what I typically do is design the surface and main landmasses in Worldpainter, then do the more intricate things, such as towns, in MCedit. If you would like to contact me faster about this you can email me at mynameisdatruth@gmail.com. Have you gotten any portion of the actual in game map completed or is it just in sketches/pictures? Either way is fine, I just need to know what I'm working with. By the way, from the pictures you linked in your initial post this map seems like it should be more than 15,000 blocks, especially if your'e planning on a lot of people playing on it. It's easy to make it bigger, so if there will be a large number of people I would suggest at least thinking about expanding it. Anyway, get back to me soon and I'll go ahead and start working on it.

1) Is any of the map done? If so, I would need pictures or the map to work off of
2) Just how big do you want it? I would suggest enlarging it, it never hurts
3) How populated do you want the map to be with towns, caves, etc.?