Alexander is a photographer at age 11 and has a bunch of photos. He's finding that Photostream is great, but he'd like a third party backup option for his pictures.
Leo says that Alexander can do a traditional backup via an external hard drive, or he can use other options like Facebook, Google+, and a paid service called SmugMug ($12 a month). Flickr is great because it now offers 1TB backup space fore free, and then he can share with friends and family. He can't upload them all at once because they have a monthly upload limit, though.
Time Machine by Apple is a good option for doing a traditional backup, but he shouldn't just rely on that. He should keep in mind that once he backs up a photo, he shouldn't delete the original, or it isn't a backup!