Each gallery is comprised of albums. You can choose which photo from an album appears on the "cover," as well as select an image to replace the standard spooky silhouette that represents you. In the beta, a few Albums that were not mine (Friends, Karaoke Party, and My Dog Spot) appeared in my list. I'm not sure if that's a bug or a feature. The check mark next to an album indicates that it's public; PSE albums default to private, which I like.