I'm glad that your going to use water bottles instead of quilts.
Just think if the power turned off and you needed water for that beautiful puppy in your picture you would have it.
I think that is the prettiest poodle I've seen, his eyes are so large.

Freezing fabric or batting isn't going to cause any damage at all. I think ice would be a better choice to keep the freezer compressor from running a lot. fabric will get cold but not return any cold to the freezer space.

I also use milk jugs.

Could you be mixing it up with putting a quilt or was it fabric in freezer or fridge before ironing.

I will keep jugs of water in my freezer. And if we get warning of a potential hurricane I make sure to fill up every little space possible enough in advance of any possible power outage so they will freeze to help keep the contents cold. I will also fill bags with ice cubes.

Back in the "good old days" my mother would starch clothes and then hang them on clotheslines to dry. When we brought them, she would sprinkle them with water, roll them up, and stash them in the refrigerator. She said that kept them from mildewing before she could get to ironing them.

I do the milk jugs or any other jug I can find filled with water & stash all over the house. We are on a private well & if the power goes out, we have no water. I also keep plastic pop bottles frozen to put in lunch boxes. When we had our Ferrets, (they loved to travel with us), I would keep a frozen pop bottle in their cage with a wash cloth around it to keep them cooled down. They loved laying against it. This works with any animal. In the hot part of the summer, it is good to do this for your outside dogs.

I have no idea, but possibly you could contact a textile museum to see if they could weigh in on this question. It would surely prevent the growth of mildew on your quilts, but maybe it would do something to them that wouldn't be good. I think that shrink-wrapping them with a seal-a-meal type device beforehand might be a good idea to really protect them from any transfer of moisture or odors - but I don't know of a device like that big enough to accommodate, other than the bags you shrink with a vacuum cleaner, and I've never found one of those that's reliable.

I definitely agree with others that jugs of water would be a better idea for filling up the space. The best thing about them would be that they would slow down the thawing in the event of a power outage. I don't have much room in my freezer, but try to keep some smaller containers of ice in there. They're great to put into a cooler for a road trip or even just to take cold things home from the grocery store in summer. Other things that I use to fill up the space are staples such as flour, cornmeal, nuts and pasta. Well sealed in plastic, they keep much longer when frozen. When I cook pasta I save energy by cooking the whole box, even though there are only two of us. The part that doesn't go into my recipe immediately gets a little dash of olive oil stirred in to keep it from sticking together, and then it goes into a freezer container. It saves time later.

This is exactly what we would tell our customers when I worked for an electric utility. It works!