What shape and type does imgs['bicubic_np'] have?
This code works fine:
images1 = [torch.randn(3, 96, 96) for _ in range(16)]
images2 = torch.randn(16, 3, 96, 96)
save_image(images1, 'test1.png', nrow=4)
save_image(images2, 'test2.png', nrow=4)