You could make one large cake (adjusting the cooking time accordingly) and cover the whole cake with the buttercream. Decorate with chopped stem ginger balls and whatever else takes your fancy, i.e. Glace fruits, walnuts, chocolate shavings etc. etc.
Really basic recipe & works brilliantly. I did mine as one cake and covered the whole cake with normal buttercream & sprinkled crushed ginger biscuit on top! - 01 Feb 2014