Sometimes we, as illustrators, are approached to do a T-shirt for _______. I really enjoy putting together a T, but most of these jobs are not going to make me rich. This is how I put a Tshirt together without spending a week on it.
I find the right free image (snake bones above) in google and run it through a vector program such as Flash or Streamline. Then I take a freeware font and shove it through photoshop's liquify tool with low pressure around the edges of the image and also other text.
Once it's done in black and white I run it through the vector program again. This gives it that "Tshirt" look, plus it's ready for the graphics people.
I try to design Tshirts for these groups that they might actually like to wear more than once for the event. I do bump into them around town from time to time.