Denim was once just a tent fabric, but over the years, it became one of the world's favorite materials to wear. Once used for practical reasons, like sturdiness and longevity, it has become a fashion staple, worn by the coolest personalities of the past century. This latter fact neatly coincides with what this post is about: celebrities in denim, but not in the way you think. It's not a post about celebrities wearing it; actually, it's about celebrities' portraits made in denim. Ian Berry…