One style that might be interesting as far as leveraging the basic map would be to use a size-reduced version of the whole map with insets for the more congested or important areas with the insets made from crops of the full-res map. Those insets could occupy the otherwise unused space around the edges. As always, the purpose of the map will dictate the final result. What you have there would be nice printed as a 36 inch high hardcopy; what I described with the insets would be more suitable for lower-resolution online use.