Kent Beck says you should report scope by picking up the stack of story cards and saying, "This is everything we have to do." Then you divide the cards into two stacks and say, "This is what we have done so far, and this is what we have left to do," showing the two stacks.
As a first approximation, this is just about right. You probably need to track the history of progress, and your management might be comfortable with just a bit more information.
Here are a few graphs. Pick the simplest one that could possibly work in your situation. Don't move up the scale of complexity unless your experience on the current project says you have to.
For each iteration, graph how many story cards exist and how many are done, on ...