Called the YouRail Designcontest, the contest calls for design submissions in the categories of "The Leisure Passenger", "The Business Traveler" and "The Everyday Passenger". Basically you just design the train interior that you want it to be like. Seats orientation, colours, doors position, etc. I wonder if anyone will remove all the seats for the commuter version... Hur hur hur.
Or if you don't feel like firing up your CAD software, you can just do up a design for the seat fabric right at the website. Or even easier, you can go in and look at what others have submitted.
Kind of reminds me of the project we did for the module Human Factors for Engineering and Design, in which we redesigned the interior of a bus. Anyway if I'm not wrong, Singapore's Downtown Line will be using Bombardier trains.