In today's tutorial, Alan said that I should write down things that I would associate with each character. So far my designs don't fully represent their specific character and so they should have some key features that we'd expect from them. Alan spoke about caricatures and how I should exagerate/show their obvious physical traits.
I have made these mindmaps for each character, where all the words can be linked to that character. As you can see, some of them have more words than others and most of them are describing the personality of the character rather than the appearance, so that's something I will continue to look at: