Printing directly on the torso would have to be done by someone with a special printer or like Raminator does which is a transfer method. Raminator can you give more details on your process for these guys so they will know about your method?
As for me I am using Poppunkmunky on Ebay, you can get a batch of 5 front and back torso's printed for $25 or 10 front torso's for $27.50 + Shipping. I am springing for Front and back to match the newer Lego torso's because I had a lego dark age, and only have the newer torso's for castle so I want them to match.