I've been learning jQuery for some time now, however i'm still more of a newbie, than a pro.

I want to make some cool feature for website i'm bulding, similar to this one (i mean working on the same rules as this one):  http://minecraft.novaskin.me - it's a online skin editor for a game. I see that they used a jQuery to make this. Probably also PHP and Ajax (i know both of these technologies at the level to make standard, basics things). I just wondering how to make stuff like this? 

How to make a field, when you can rotate your skin (based on a png file), and also draw things on it? As if like kind of a graphic editior, but the specific one. How to do it? Where should i begin?