I have a brand new fridge that I am currently storing in my garage as we are going to sell our house/move. Is there any danger for the fridge to be stored in an environment where temperature can go below freezing?
Yes, there could be a little harm.
For starters, your water supply to the refrigerator could freeze. A fix for this would be to insulate the water lines and getting a line heating strip:
This would be run right along side your water line, or wrapped around the water line, and would prevent the water from freezing inside the line. This is very common with water drains in refrigeration systems during defrost mode.
Other than the water supply to the refrigerator, there is no real harm outside of whatever your contents would be inside of the refrigerator, may freeze as well. If the ambient temperature is colder than the temperature inside of the refrigerator - then the refrigerator would not refrigerate since the thermostat would be satisfied.
Mechanically that wouldn't pose a problem. However, it wouldn't prevent items within the refrigerator from also freezing.
If you aren't going to power the refrigerator at all, then blow some air through the water fixtures to ensure there is no water still inside the water supply of the refrigerator itself. That will ensure nothing freezes and bursts within the refrigerator.
If you aren't going to store anything you don't care about being refrigerated inside the refrigerator whenever it is turned off, then there is nothing foreseeable that could harm your refrigerator when being stored within your garage, freezing temperatures or not.
However, there is another thing, in terms of refrigerators, to consider: mold growth. It is not advisable to store a refrigerator with the door closed - and not running - for long periods of time due to the growth of mold inside the refrigerator.
If that isn't a concern of yours, then you can clean out mold growth inside of your refrigerator by submerging a clean rag into baking soda cleanser and wring it out. Wipe the entire refrigerator and freezer out with the baking soda cleanser. Do not use bleach!
Refrigerators like to be cold. (I feel completely stupid writing that.)