Just wanna give a thanks to everyone here for posting such useful information. This allowed me to understand what components make up a good picture of a planet.. I'm pretty very young in my 3D career, so I thought I'd take up the challenge of seeing if I could make a nice earth render using the Blue Marble data. In this render the textures are only 2048x1024, and I'm still working out how to properly do night-side lights.
rendered in Maya 5.0.1, using Maya Software renderer.