Here's what people have said about working and interviewing at Card Factory.
Card factory tshirt
They do accept things like piercings, as they didn't ask me to take my ear ring off, but you have to wear smart black trousers and smart shoes, but you are not allowed to wear jeans or trousers with more than two leg trousers as it apparently give the store a scruffy image I believe, and your not allowed to wear trainers as well.
You are also given a standard blue t-shirt with the Card Factory logo on the shirt that you have to wear at work, though you can change into a regular shirt when your shirt if finished. You also have your own badge with your name on it that you need to wear on your shirt as well.