Image Classification on non real images
This question is slightly philosophical, but can be explained in this way - If you model is trained on real photographs it will likely not generalize well to things like drawings unless they are photorealistic or contain the features that the model is using to classify the images. You would likely have to include drawings in your training data to be able to do this effectively.

An interesting project leveraging Machine Learning that may have some relevance to what you are talking about is a recent Google project called "Quick Draw!" (link here) You should check it out. Essentially, it takes input of human drawings and outputs a classification label for what it thinks you drew.