Custom Shirt/Jacket Sites?

Hey, does anyone know of an intuitive online site that lets people submit shirt designs? I have an idea, but it can't be accomplished with iron-on designs or, like those other sites, simple factory images pasted on shirts. I want something professional and original. I'm not looking to throw down a ton of money, but my design is much more than what most custom sites offer. Any ideas of a site that allows shoppers to order specific designs as opposed to a list of select images?