I don't know of any preferred image type. Do what works for you, I guess. I'd look to just outline the concept in detail, rather than doing a lot of work on specifics, if you know what I mean.
I just wanted to give pictorial examples of what a change in month means, not really play maps to play on, but how what happens each month effects the "story" for the next month.
I already got a 1 page (printed) HTML file full of stuff written down so far. So just need to refine and add some more and get the image examples thrown in.
Want to make sure all parties understand the concept so they can play with it further.