Here's the pic I used. I found this on the internet. So... is the rendering mine to do with as I please or...?
The original image, unless specifically put into Creative Commons where derivative works are allowed, is covered under copyright. That being the case, unless you get permission (in writing) from the photographer, you would be intruding on someone's "right to copy."
Realistically, you are pretty safe using a web image for learning to illustrate, but I would avoid using the image to make shirts for resale, offering it up as stock illustration (istock, etc.), or using it in a product for a client.
iStock has a much better explanation regarding derivative works,
here.
Great illustration, btw!
Cheers!
-g-