Here are some options, depending on the context:
General:
* A field of ice (for a large expanse)
* A sheet of ice (for a flat surface)
* A mass of ice (for a large, undefined amount)
Specific:
* A glacier (for a large, moving mass of ice)
* An iceberg (for a large piece of ice floating in water)
* A pile of ice (for a collection of smaller pieces)
* A block of ice (for a rectangular shape)
Ultimately, the best choice will depend on the specific situation you're describing.