My son loves to play this game. As he's 6 and a train fanatic, he can sometimes be hard to please. So this is his list; I'm just hoping you make them.
Mountains with and without tunnels
Birds, dogs, cats, and general wildlife
More city stuff -i.e. traffic lights and signs, more fences, more house and building types like museums, banks, Cafes, office building (because you have business passengers but no business office), cranes and construction vehicles, quarry workers, buses, pedestrians that are not passengers, a school, water of all kinds but especially rivers (because "every train builder is happiest building bridges"), and etc.
Church and wedding decorations for the wedding passengers
Trains shaped like roller coaster cars, metro trains, steam trains, freight trains, (I'm sure you get the idea).
Cool landmarks like Eiffel tower, statue of liberty, space Needle, and even new ones that "[I] don't know but will for sure be awesome to blow minds".
More light up stuff for night time, even the safety glo colored tracks, or stars or a moon you can hang in the sky
Elephant for the circus and clowns.
Ocean with docks and like "the boats that can put trains on them", whatever that is.
Ability to change the graphics on the floor/ground like to grass in one spot and cement in another but at the same time
I know that there's more but I forgot. 馃
Now, I understand that not everything is possible or even coherent as an idea. But I asked. After all, you guys made my son think you're "definitely the smartest person ever, probably Santa." So Santa or not, thanks for making him happy. And I think some of the things would be cool additions too.