Cute dog sweater. And if someone likes it (and I bet someone will), they'll measure their dog and see if it fits. Dogs, like people, come in all sizes, so any size should work for some cool dog somewhere!
A former coworker has a chihuahua, and they used an old sock for a sweater--worked great. In fact, in addition to keeping the dog warm, it acted as a doggie straight jacket, too. The dog would be bouncing off the walls and acting horrible. Then they'd put the sock on him, and immediately he'd mellow out!
Perhaps you could market your dog sweaters as both a coat and a behavior modifier!?