“Many good ideas will not work well on MNIST (e.g. batch norm). Inversely[,] many bad ideas may work on MNIST and no[t] transfer to real [computer vision]” – a tweet by François Chollet (creator of Keras)

So - please, anything harder (or rather: more relevant to deep learning). At least images in CIFAR-10: https://blog.deepsense.ai/deep-learning-hands-on-image-class...