What sites can you use to make customizable t-shirts that will let you customize the entire shirt?

I've looked at a couple of sites, like cafepress and printfection, but none of the sites I've tried will let me customize the entire shirt. They only let me work with a section in the center. Does anyone know of any sites that let me have more freedom with t-shirt designs? Paying for this service is not out of the question, but free is preferred.