You will have at least one "long row" in a Descendant Chart. I know you want an Image in your tree, but could those images be part of the long row issue? As far as I know, the image would be on the Left side of the box.
Just a question about the images, Do you have a high percent of people with images? I am not sure that I would try images in a descendant chart. There are other charts where an image would be more useful.
Is the background you are using something you created, or a background that Family Tree Maker provided.