You know your sister better than anyone else. You did grow up together after all. Your sister is turning 40 and you know you must give her a gift that lets her know the best is yet to come. Photo gifts are a great way to remind her of some of your favorite memories together. You could also go in a more fun direction with your 40th birthday ideas. Search for something that jokingly tells her she's old (only if she has a sense of humor!) like reading glasses or a walking cane. These gifts can make their special day just a little bit better and remind your sister that she's loved by you.