Hypothetical Question!

Accessories are always nice!
I could think of:

• additional wagons, coaches, cars (more coaches for JR trains - for example blue coaches for steam trains, additional express coaches for Gordon, James etc, Old Slow Coach without the flags, Emily's coaches, Hong-Mei coaches An An and Yin-Long; Lucy, Jemima and by all means - Beatrice for Skarloey Railway!, and many more...);
  
• additional middle cars with sound;
  
• (dummy) front cars with front hook for commuter trains (it would be nice to make 2 or 3 train combinations);
  
• appropriate road vehicles, industrial and other vehicles that are connected with the specific train (many railway operators have also a company bus-fleet, for example, so it would be nice to have a company bus with a circle of road-pieces as an accessory);
  
• additional faces for Thomas & Friends (a face for Henrietta!);
  
• appropriate Plakids (for example a Saitama Seibu Lions Hockey Player Plakid will go great with my Seibu 9180 L-Train!);
  
• other railroad accessories, stations, other buildings, bridges, tunnels, docks, little lakes, volcanoes (!) and other stuff that goes with the specific train (like Kamakura Buddha with Enoden)...
  

I could go on!