I think you can consider one single image as a large corpus of data, in the same was that you could train a simple Markov model from a large paragraph of text. It doesn't matter to the model whether the original text was 500 words in one piece of text, or five 100-word texts.

It's mostly looking at local regions and seeing what guesses it can make about the next region given one region. (If I understand correctly).

Ahh I see, these are some resources that should help you.

The original Neural Style Transfer paper should help you understand the loss functions involved: https://arxiv.org/abs/1508.06576

The paper introducing Real-Time Style Transfer is basically the algorithm used here: https://arxiv.org/abs/1603.08155