An idea that I had for the layout of the page were you Add a Post, Page or whatever your custom post type is.
First context; currently the layout is setup so that you can have 1 or 2 columns. I often find myself wishing that the box where you enter the entry content was wider than it is. I've tried using just 1 column but then everything else is so far apart and all your other boxes that just don't need that much space are wasting space.
My idea/suggestion is that it would be nice to have another page layout option where the entry title and content are 1 full width column right at the top of the page and below that you have 2 columns. You could even throw in the ability to move other boxes from the lower 2 columns into the full width column.
Hope this is a helpful idea that inspires someone to make it happen.