For moons I would use some NASA pics. They are all in public domain. A good site to browse for them is here:
For the planet basically what you need is a sphere with texture mapping. Celestia is good for this or you can use a 3D app like blender or something lighter and simpler. All of them can do spheres no problem. There is sphere mapping as a texture style so you just sphere map a texture onto a sphere, add a few light sources, position camera and render.