I'm not saying it to be mean or anything. I love vectoring, but I would never sell them on a shirt, especially if the material is owned by Nintendo. However, if you were to make your own fan art not based off of a previous image, you could possibly sell that, although you may need the company's consent. (I was thinking how they had those Bioshock shirts on Threadless, but it was a part of a contest and I think the company was involved).