We used a lovely home-baked bread that my husband made the night before, as well as..
Mini Shortbread cookies for the engine's window
Chocolate covered cookie rings for the wheels (the original used Oreos)
A glace cherry for the red light
Pretzel sticks for the ladder
I had prepared an example beforehand, and placed all the little bits and pieces on individual plates for the Little Joyfuls to build their own engines.