Thanks EAdams!
I have just done an update making it work even better with non square images. It is now possible to change the horizon line. This way it is possible to avoid the feeling that some tree may look someway in the air when using wide images.
I also added the chance to make the base of Mount Fuji wider and a bit blurred (I saw that, with the basic settings, when using dark colors for the grass or the sky, the base of the mountain was too neat and didn't look natural).
Another adding is the chance to select, for the results where the sun appears, to have the sun or the stars in the sky.
Here is an example :