I don't follow the logic there You can't customise each page yet you are willing to go and insert half a dozen breaks on each page when an image isn't present? Why not just add a an extra class to the column on pages without images and set extra top padding equal to the image's height.
As others have mentioned breaks are structural html elements and not to be used for making space - that's CSS's job. Breaks are used for line breaks such as between addresses, poems, song lyrics, form elements. They are not to be used for making space of for paragraphs. Also finding consistency with formatting breaks is not that easy so you can't easily create an exact height and indeed breaks are ignored if they start or end in a parent tag.
However, as others have said it would be helpful to see exactly what you have got in order to give more specific advice.:)