Today freezers come in all shapes and styles. And they can all develop odors. It can be tricky finding the smell and then getting it removed.
The most common smell is from food. Food not stored properly will cause the freezer to smell. The odors can be very strong. It can even make the ice smell and taste nasty. So it is important to make sure every thing in the freezer is stored correctly.
If the air vents in the freezer are blocked, it can cause the air in the freezer to get stale, and start creating smells. Make sure when placing food items in the freezer you do not block the vents. The freezer needs proper air flow.
Of course any new freezer will have a plastic or chemical smell, from the factory. All you need to do if possible is to leave the door open and let air in before you connect power and your water supply. Over time the smell will leave.
To clean and have a fresh smelling freezer try this mixture, one tbsp of baking soda to one quart of warm water. Use a sponge and clean the freezer surface. Leave a box of baking soda in the freezer to absorb any future odors.