Anyways - I find it sad that people would just take art even when it states "don't use em".
I'd rather have my biscuits kicked by three whatya-call-em rather than have my life stolen.
It's just called Sugi style, named after Ken Sugimori, and I'll assume you know who he is haha. It's not extremely hard to learn, but you might have to upgrade from Paint.net to get it. I'm not sure though, because I haven't used Paint.net. But here's a tut for Sugi-style: http://browse.deviantart.com/?qh=§ion=&global=1&q=sugi+tutorial#/d1imuvq
You already draw pretty well in the Pokemon style, so it should be no problem for you to get Sugi down. And after you learn the basics of it, you can put your own touch to it, like I do: http://optimisticxpessimist.deviantart.com/art/Fakemon-DEX-Snyper-167578588?q=gallery%3Aoptimisticxpessimist%2F4465615&qo=1 or http://optimisticxpessimist.deviantart.com/art/Fakemon-DEX-Berpup-163292565?q=gallery%3Aoptimisticxpessimist%2F4465615&qo=7
The appropriate line size is actually 1pt. It took me a while to figure out [You can see only Snyper has 1pt lines, cuz he's my newest one I've colored haha.