first off welcome to the aomh forums.
my advice would to practice.
have a good long look at the scenario design library. download reyks editor.
have a look at other peoples wprk in the pinned eycandy thread.
then make up your own ideas and make your own dam map!
i am almost certain that you will not get a volenteer to make you a map for a credit mention as they could just as easily submitt the game themselfs.
good luck.