images_dir = '/home/roman/Рабочий стол/images'

products =list( Product.objects.all())

categories =list(Category.objects.all())
images_list = []

for address, dirs, files in folder:
    for file in files:
        images_list.append(address+'/'+file)


 for product in products:
    ...:     initial = ProductImage.objects.create(product=random.choice(products))
    ...:     file = random.choice(images_list)
    ...:     initial.image.save(os.path.basename(file), File(open(file, 'rb')))
    ...:     initial.save()