Yes, I guess you could use a masterpiece and only tweak a few things to show the passage of time. We would like to see a lot more effort however, so the new piece should almost be an entirely new map. That is one of the core rules. You should submit a map that you made specifically for the challenge.

This is a special challenge though, so let's see how it turns out when people are allowed to take a previous map as the basis. One thing I have learned is that the people on this forum act very grownup. Also, we are not giving away Oscars or something...

If I am wrong, there's even an award for messing things up

Thanks for your comment by the way.