Rapunzel's should be a flower... IF possible XD like the scene when she cured Eugene? I don't know if its possible, but I guess it would fit her since "she is a flower" (like Gothel used to call her) or maybe you can take Pascal out and make the Patronus of Rapunzel a chameleon nwn
I was thinking phoenix, actually. Its not unheard of, cause that's Dumbledore's. But yeah, i don't think a flower is suitable, considering a Patronus is mostly based on and moves like a living creature...
If you are going to draw the big four with their patronuses (or would that be patroni?) I love the arctic fox choice, it fits Jack perfectly . Perhaps you could take the His Dark Materials route and consider placing their Patronuses with their character? You know, Rapunzel could have some type of dog, since she is very loyal, etc, or just have the patronuses with their animals that they are connected to in their respective movies, (I.e. Hiccup - Night Fury, Merida, a bear, Rapunzel, a chameleon?). Of course, it is all completely up to you to decide what you want to do, but those could be some possible options to consider. I love the stance you chose and the blueish stuff that the patronus is made of reminds me of the will of the wisps in Brave, Very nice pic! Please draw more. Sorry for the long comment, but I like the idea. I also adore foxes.
You should do the rest of the 4. Hiccup, Punzie, and merida. i think toothless in human athro form should hav one too. man tht would b intresting. would his b huccup or a creature tht resembles hiccup.
I would have picked a Snow-Shoe Hare... in connection to the snow bunny he used to get Jaime to believe in Bunnymund again... but I like the Fox, cause of it's playful and trickster like nature! Very Jack! ^_^