Not saying that some artist might not have some free time ingame. just saying it would be a good thing to make when it really come's to making art.. ok imagine this.

click on the site and you see a 2d or 3d shaped tori. then click on one of the joints or body and it gives you the upload link for the art you want to put on it. it processes it just like you would when uploading a texture to check ingame..

finally, it shows you your finished project. then you would move it around and see if there's any mistakes on your tori or not if needed.

Easy as that, you could either save the tori as a whole png or whatever. Or you could right click on one of joints or body parts and save to show the thread what your trying to sell....