This may sound like a cliche but perhaps you could try to emulate the high-line's success? Lush up the linear surroundings with greenery and landscape and call it the green line ?

Alternatively, it could pay homage to the past by converting its use to a cultural center/gallery.

What do you think makes a space for imagination? 

Is crafting some grand space any more effective than just putting up a sign that says "Space for imagination"? Convincing he occupant about the intent of the space is often easier than actually creating a space that meets that intent.  Look at all the churches that hold service in lackluster spaces.  The idea makes them what they are, not the space.

So, what are you going to do to a train station, a thing that served an entirely different purpose than promotion of imagination, to make it do what you want?  

I'm going to assume you're a student.  If that is the case, you can claim whatever you want.  Just have some sort of logic behind it.  You'll be fine. 

Is the train station abandoned? Does it have any sort of history? Turn it intk a museum that explores the past present and future

Something something the physical transportation that trains provide provides a metaphor for imagination as mental transportation...

I'd start there.