The above was very early concept sketches for what would later become the final design, just to get the junk ideas down on paper to rule them out.

Then came actually designing/rendering the milk bag in Adobe Illustrator (early concepts of eyes and mouth shown below). To help me with this I took a photo of a milk bag which I positioned similar to the final image on a chair in my living room. The photo has since been lost unfortunately. 

After further tweaking and revisions suggested by the client the eyes, and mouth were changed, as well as where they sit on the bag. Below is the final art which appeared on the shirt.

Here is the final with where the image was positioned on the shirt. Thanks everyone and I hope you enjoyed this post.