There are two inputs to the Planet: "surface shader" and "atmosphere shader". Using the planet in the default project as an example, all of the shaders that affect the colour and displacement of the planet's surface are fed into the "surface shader" input. Only atmospheres and cloud layers connect to "atmosphere shader".
The same thing applies with the new planet you created. The connections might be found in the planet's internal network but the same general rule applies. The Image Map Shader (either on its own or part of a network of other shaders) can be will colour the planet if you connect it to "surface shader".
You don't need to put them in the internal network if you don't want to. If an input plug is connected to a node in the internal network, the plug will show in the internal network. If it's connected to a node outside, the plug will show outside. If you want the shader outside but you can't see the connection plug outside, you can make the connection using a menu. You can right click on the plug and assign any existing shader or create new a shader and assign to that. You can also do the same thing from the planet's Parameter View (the window that comes up when you double click on the planet node). On the planet's Shaders tab, you can assign shaders to the "surface shader" parameter using the "+" button on the right hand side. After connecting to a node outside the internal network, the plug will show up on the outside.
Matt
