Well, that's the best thing about an image editor with PdN's features, and ease of use! You can't really make serious additions in something like Photoshop, as it is too hard for the average user, and you can't change images in MS Paint, unless you want to draw a square, or an ugly, aliased, jaggy line...
Actually, I want to go on and put more into the picture, but I'm inspiration-less... I want to put in a good-looking planet, but I can't work out how to do it. I know I need to use S3D to make the sphere, but I can't seem to make a good texture... Can anyone help?