One day in a drawing class I teach I was talking about "Scrap". Scrap is reference material that almost all artists use somewhere in their creative process. It used to be file cabinets full of pages clipped from magazines. Now, artists have is so easy with the wealth of material available on the web. Instead of magazine clippings it is now digital imagery. I have several terabytes of images collected, mostly sorted, and cataloged.
Student artists often have a hard time knowing what reference is for and simply copy images they use. Not only is this sometimes ethically questionable if you are using an image that you did not photograph but it is not the way that scrap should be used. It should be referred to and not copied.
So, in this particular class, I gave each student a different image of a creature created in Spore Creature Creator ( http://www.spore.com/ ). If they simply copied the image they would have a very simplistic and boring drawing. They had to "refer" to use the image to and draw a creature based on it. I generally try and give assignments that I don't mind doing myself. I could not resist myself and here is my result and the original image.