Funny coincidence. I believe that what you are mentioning falls exactly under the topic I posted a few days ago ("Horizontal and vertical rulers to help design quick and consistent dashboards") to which I did not get any answers.
I am very surprised by that actually as I expected James, Joe or Richard to pick that up. Maybe this is a brand new kept secret feature that will be unveiled at the conference when they introduce 6.0....:-)
I really hope so.
I just recently had some luck with fixing my problem. I used a container for the "header" section and set the size from automatic to an exact size. This is my “template”. Then I can duplicate the dashboard template and add content. This seemed to shape up all the out-of-wack images.
This works for simple dashboards, I'm not sure how it would work for more complex dashboards.