For toppings use mini M&M's, coconut flakes, frosting, cake glitter, and sour patch people.
For larger houses, I built the house on a small dessert plate.
For super mini houses I used the mason jar lids covered in foil.
I frosted the approx size of the little houses to lay it out on.
I found mini candies, sour patch people and coconut flakes to decorate, add more ideas of course to make it your own. I used basic frosting from the store and used the smallest fitting on the piping bag keeping the frosting cold as possible when not in use.
Here is the larger of the mini Gingerbread houses.
PS If you get real create make a hanger into the roof and frost over the wire and you can turn it into an ornament.