i have a photoshop plugin somewhere that allows you to create numerous layers and textures for planets is really good.
all flat aswell so all you need to do is uvmap it to a basic sphere in your prefered 3d app.
will dig out details if anyones interested.
also have a wicked space skybox generator aswell.
although saying that, plug that type of code into skyline and weve got star citizen style gaming at our hands
