The old stand-by - Luther's seal and its meaning. Option. Use double-stick tape and attach it to cardboard and cut into a 4 piece puzzle (for little ones).

A few years ago I created a Wittenberg Church Door out of a big piece of foam insulation. I made sheets of paper to look old (rolled edges) that started with "I Believe" followed by a series of lines for the children to write their belief statements (little ones can dictate). At the bottom of the page, I wrote "Here I Stand". The kids could then literally nail their belief statements to the door, just like Martin Luther. I also printed off a copy of the 95 Thesis (translated into English) and nailed them to the 'door' as well. (attachments)

I also have "The Adventures of Martin Luther - Big Book".....published by Concordia Publishing House (unfortunately no longer in print), that I have found helpful. 

I have written a script which is  dialogue between Martin and Katie Luther, with a couple of inserted statements/questions from the classroom leader, about the Reformation. I have two young adults what will be presenting it to our mid-week evening class (grades K-4). (attached)

Hope that is helpful!