I dunno if you all are familiar with a software package called "Vue 9" from "e-on software"? in that software you can create environments from rocks and plants to terrains and ecosystems, clouds, weather, etc, and it also has an option that will take make your scene into a spherical planet, you then export the scene into a folder take the textures, import them into a singular file in Photoshop in different layers, and then export it or save it as a .dds file, with a tool download from nvidia... import on sandbox and you have your planet with atmosphere, clouds, terrain and anything else you want... seamless textures, bumps, normal maps, everything...