Someone explain to me what an imperforate hymen looks like?

Easy: An imperforate hymen means the vaginal cavity is closed. You would not have visible bleeding with your menstrual periods. I suspect that question has been answered for you by 40 years old. If you are talking about someone else, then the vaginal opening would not be open below the opening of the urethra (where your urine exits).

Image: Image of an imperforate hymen (compliments of medical illustrator - frank netter). http://www.bing.com/images/search?q=imperforate+hymen&qs=n&form=qbir&pq=imperforate+hymen&sc=8-17&sp=-1&sk=#view=detail&id=09753d4af6aaf890bd36554c04a925d5cc28602c&selectedindex=44.