Environmental problems

I trying to create an iceberg for a project I'm currently on. Should I use lofted curves or should I create my environment using topographic maps of a real iceberg and b spline all the way.....

it depends on what you need. I would get a diagram of an iceberg.. or draw one myself.. or just sculpt it in Maya.... depends on how real you want it [which you will need reference]
Most likely I would make it in polygons... since it might be easier to make some hard angles associated with ice.

if it was to break apart inthe animation. I would plan those into the model.