We decorated the room with blue, red, and green streamers and balloons (for Thomas, James, and Percy). We had some Thomas plates and napkins, and then just used blue, red, and green ones
to fill in the gaps.
The tablecloths were also blue, red, and green. For games, my husband made a big picture of James for them to pin the nose on, but as kids were wild, they just threw balls at it instead. He also made a big train (side view) and cut holes out of it to throw "coal" through. We also got coloring sheets of Thomas, James, and Percy off the web so that they would have a quiet activity to do. We put one of son's train engines at the end of the food table, and lined up loaf tins behind it for a train, and served all the food out of them. We made a train cake using loaf shapes for cars, and made an engine out of stacked wafer cookies. The serving board was decorated with icing for grass and water, and used upside down sugar cones for trees. Each box car carried a different "load" of candies from the bulk food section, such as chocolate, foil-wrapped sports balls, candy blox, and ju-jubes. I also made candy trains for the kids to take home, using Lifesavers, caramels, Hershey's Kisses, and peppermint wheels.