Quentin Massys John Tenniel
Ugly Duchess has quite a history in illustration. Sir John Tenniel created her image based on the portrait 'A Grotesque Old Woman' (1513), by the Flemish artist Quentin Massys. Not exactly the same, but the influence was very obvious.
Lets look at how the Ugly Duchess is described by Carroll; in the first scene there isn't even a hint of her appearance, she is full of pretence and we can only imagine what her true character is like by looking at her actions, analyzing her dialogues and speech. Such an ignorant and unfriendly person, she is a persistent fighter - she doesn't pay attention to the pepper in the air, or the dishes thrown at her. She makes her remarks with a "sudden violence". This is all that is said about her in the first scene. Plus, of course, an absolutely cynical attitude towards the baby.
Leonardo Da Vinci "Grotesque old woman"
Another scene where the Duchess is acting - "Queen's Qroquet-Ground". Here, her behavior is quite different, her speech when addressing Alice has now become rather somewhat sweet. We see an experienced court-lady, who can speak very sweetly if she feels an importance of the person that she speaks to (we know that Alice was invited to the Queen's Qroquet-Ground, and that means something). We remember how she treated Alice when she (Alice) was just a stranger to her. As a matter of fact, she is trying to be so sweet that she is ready to hug Alice around her waist (which she doesn't do being aware of the flamingo in Alice's hands). Here is the first time we get a few words regarding her appearance. First of all, she's very "ugly". Secondly, she has an "uncomfortably sharp chin", and lastly, "she was exactly the right height to rest her chin upon Alice's shoulder"- so she wasn't taller than Alice. And that is all that is said about her appearance.
I wish to point out, that Sir John Tenniel's Duchess is undoubtedly ugly, but her chin is quite far from being sharp. Many illustrators followed the tradition of Tenniel's illustrations. Ugliness of the Duchess (in this tradition), is straightforward - it is an ugliness of old age; an old, wrinkly, male-shaped face. I think that this way is too cliche. From my observations, the human face's attractiveness is quite a tricky subject. It is very often that beauty and ugliness differ due to the existence of a small feature(s). The perfect example to me would be the famous movie star Ms.*, who is beautiful because of the camera, makeup, and a properly set up light. But every now and then these conditions (or one of them), fail to perform their function. It is at these moments where you look at her and realize "Oh my God, she's plain ugly!"
Generally, when drawing my version of the Duchess, I didn't invent anything. My Duchess is taken from real life; this type of face, nose, etc... That kind of person everybody has met. By the way, the personality of this type of people is usually the same. So I'm guessing whether Lewis Carroll would have approved my version of this character. At least, Carroll didn't mean the image of the Quentin Messis's portrait when he wrote his Duchess.
The Ugly Duchess personality was carried out into the second book, but into a different character; the Red Queen. They have a lot in common, evidentially the same prototype was used for both the characters. This is meaningless to most readers up until they start reading the second book, however to an illustrator who wants to understand the character more deeply, this relation is quite evident. They are both addicted to using hyperboles: when Alice said "... I can't quite follow it as you say it", the Duchess replied "That's nothing to what I could say if I chose", compared to Looking Glass; when Alice said "...I thought I'd try and find my way to the top of that hill", the Red Queen answered "When you say hill, I could show you hills, in comparison with which you'd call that a valley." Both of them also like to teach Alice, and seek out the moral in every situation, conversation or anything at all.