Alas~! My version of the Mad Hatter. xD
I used a base for the original cosutme design, then did it in my own style. (honestly, I like the base version better. xD)
Anyway, I've decided to give him my hat. Because I've always wanted to use it on a character. <3 So I added his card to it.

A lot of the fanworks I see get rid of his white hair (whether the white hair was Disney's idea or was in Carrol's original work I don't know, but I like it, so I kept it.) I also gave him a black and green tailcoat-type jacket (with wider tails, you'll see in later pictures), and a red vest. An ascot by itself, because he's like that.
I've also decided to give him either white or green pants instead of my original thought of red ones. I'm thinking maybe I should give him white pants with Green decor, or visa-versa, because I like to accent the colors he's got and balance the scheme of the costume that way. ;D Which is why I gave him a red vest instead of red pants (originally there was no vest).

As far as personality is concerned, I'm going to read the original novel to get a better grasp on his original character, but I wanted to make him the type that has a child's curiosity with a psychopath's thought process. He's very cheery and playful with a witty, rather nonsensical sense of humor, but he's seems to have quite a bit of mystery to him to me. So I want to use that and give him a bit of a sinister air blended with the hilarity of his character traits.
My goal is to make the audience see him as the kind of character that could kill you so seamlessly you wouldn't even notice you were dead until you were looking at your emancipated body from the other side. After you were through laughing at his joke, of course. Which, you now realize, probably didn't make any sense in the first place, which makes you ponder why it even made you laugh at all.

...Maddening, isn't it?