To show our images in a reversed order (with the newest at the top), in views I wrote:
images = reversed(list.image_set.all())
This created a problem when you're trying to use len(). I was trying to find the length of the queryset to implement a Facebook-like infinite scroll.
We solved it by creating a QuerySet that reversed the order before outputting:
images = list.image_set.all().order_by('-id')
Hope this helps anybody who had the same problem