Mini-planets are a fun and interesting variation of more traditional panoramas. Rather than combining the images in a grid-like layout, the images are stitched to form a circle. If you have a full 360 degree by 180 degree image of a scene, it is easy enough to create a mini-planet using software that simply remaps the image around a circle.
However, to create a mini-planet that is creative, fun, and looks good can be quite challenging. Like most photography, it requires being able to envision what the final result is going to look like before the first shot is ever taken. This includes understanding and imagining what will happen to the image as it passes through each step of processing. For mini-planets in particular, the scene being captured by the camera is going to be distorted quite a bit.
Here are some more mini-planet photographs that I have taken.