I have set a standard of posting all my photos at a 16:9 ratio. I was just looking at my cover photo and the image displayed is a horizontal slice of my photo.
It looks like the crop begins at the top left corner, so the emphasis in the photo is on my ceiling. I would love for the crop to be taken from the center of the image.
Another option would be to give us specs and let us create an image specifically for the cover image.