Thinking about stuff

They have these machines that take a photo and "print" it on a cake. If I owned a bakery and you wanted me to print a graphic pornography image do I have the right to refuse? Can I just say no to a cake shaped like a giant penis or a par of boobs? What I'f the local Skinhead club wants a swastica in red icing? Is there a line a business can draw? What do you think?