hello Cartographers,
my name is Jaekaido and i am new to making maps while i can reproduce maps based on tutorials none of the maps i make look right to me. i have seen several maps here on the forums and must say i want to make maps like them. particularly the town and city maps. i am looking to create naturall medieval towns and cities, but am wanting to start at the world level first as the terrain is going to help my process of world building for D&D. i am trying to figure out what dimensions the earth is cos my world is earth sized and functions very similar, though time is different as my game is base purely of of 7's. Anyway, for a 2d map of an earth sized world what should the dimensions be as i want to have detailed mountains and rivers along with islands, continents and even plate tectonics. my problem is that i dont know where to start i though that if i started with the plate tectonics that would lead me to the continents which lead to mountains, canyons, volcanoes, and islands. i will be running a series of games in this world all from different campaign settings that exist in the world. i use Photoshop cs3, and have a good understanding on most of the features. so for my first couple of questions.

1 how tall and how wide should an earth like planet be?
2 are there any easy ways to create natural looking plates in Photoshop?