Thank you everyone!
DIANNA, can't give much advice as I'm really new to cover art myself. I will say that always give more room around your focal area as you can. The image can always be cropped down, but, you can't add in more art background if it doesn't fit the format or just needs more space for title and cover type. On this one I tried to make the background generous in my initial drawings for that purpose. Then, when I transfered it onto my painting panel, I added another inch all around. The background elements continue to the edges, but, all the important elements of the art are contained in the center. This can be cropped way down to a horizontal rectangular format, or a taller narrower vertical format.
This is shown cropped to a vertical narrower format.
And a horizontal format.