Hello!
You might try looking here:
www.vietnam.net.pl/M55mod3en.htm
On this page I describe building a styrofoam diorama base.
As for the chain - try looking for some real-life chain and just try to duplicate what you see - works best IMHO. It probably would be natural steel, weathered but not too much rust - it would be constantly grinded away while the chain moves.
Hope it helps, have a nice day
Paweł