"Unprofessional" only makes sense in the context of some particular profession. Many English dictionary definitions even explicitly mention something like "the expectations of a particular profession." I'm pretty sure there still are professional standards for doing graphic design work for a punk art organization. And you wouldn’t say that a plumber is coveralls is dressing unprofessionally. The word “unprofessional” doesn’t just mean “anything that’s different than a stock photo of a banker.”