T-Shirt/ hat design help?

[Pee_and_Ski]

so i am working on a project for me e-commerce course and we have to make a website that is fully functioning to sell a product, my group is selling t-shirts and hats so i am wondering are the any programs that are good to design shirts and hats? i would love for this program to be free too.
thanks guys +K too

 

[Troy.]

Photoshop (pirate)

or Skitch (free)