Lin,
Something like the "image and border" tool which acts globally. But the "image and border" tool is too clumsy in that it puts a border on the outside of an object and necessitates a "compensation" via the canvas settings. A simple line or border inside the confines of the Slide sitting on top of all other objects set globally with the ability to switch it off on a slide by slide basis is what I would like to see.
Barry,
Yes, it could be developed to produce distressed edges and other effects such as Black/White/Black etc.