While I finalise the planet, I thought it worth sharing a link that helped me break planet rendering down into manageable chunks. Robert Simmon created an excellent simulacrum of Earth using multiple rendered 2D and 3D elements composited in Photoshop.
http://earthobservatory.nasa.gov/blogs/elegantfigures/2011/10/06/crafting-the-blue-marble/
The attached image shows the elements I am working with to put Chriirah together, along with still to be added atmospheric effects.