Thanks a lot for all the elaborate answers. I'll take everything here in consideration when designing my world map, and then regional maps.

The world is the first in a universe that I'm designing - the world from where humans originate. It is supposed to be a huge garden world (a super-earth) with different sentient species that split off from the human evolutionary line that spread across different continents that are isolated for a long time until advanced shipbuilding is invented. I would design the world and its inhabitants in various stages, starting with when its sentients inhabitants are still relatively primitive and sparsely populated, but advanced enough to create a wide array of civilizations that are diverse in itself - think 3000-6000 years ago on Earth. The world should be green in general, but I would like all different types of landscape to have a place; barren desert to deciduous and evergreen forests, rainforests, jungle, tundra and savannah and grasslands, marshes, ice, everything. I would like to design the world in different stages, until they become spacefaring and start colonizing other worlds.

It's a world, ultimately universe, building exercise for it's own sake for now, and also to set stories in. It's proving a lot more complicated than I thought. Ecosystems are complicated things. I have been delving into wikipedia for a few weeks now and reading at the local library. It's overwhelming to think of all the theory involved in creating a realistic, diverse landscape.

The most advanced world making utility that I have found, Fractal Terrains, creates unconvincing worlds to me. They are too monotone in climate (rainfall is the same just about everywhere, except extremely high altitude, and temperatures are also not varied enough for me by far), and the shapes of the continents don't make sense compared to those on Earth that sort of fit together like a jigsaw puzzle. It also does not seem to take into account that some parts of the planet receive a lot more starlight and how the atmosphere and ocean currents influence climates. Those are just a few of the major considerations. Also, all landmasses always rise above the sea for hundreds of meters right at the coast and have a tendency to rise to thousands of meters shortly. I don't want that. A lot of the lands should be relatively close to the sea altitude-wise.

So I will have to use my truly most advanced available utility to design my worlds: my brains, and design my world by hand in Photoshop. I am glad to have found this place though. There are some awesome photoshop tutorials here, and there seem to be a lot of great, passionate people that don't mind helping out.