How do I make a material for a sphere in photoshop?

I am trying to make a 3d earth, and I have the 3d modeling done, I just need to know how to draw on the sphere. Since I use blender, my plan was to make the planet,which is done, and then unpack it in unity and add the materials to each piece. I need to know how to make an image that looks good when you place it on the sphere. My options are also not limited to photoshop.