Photo Stream Empty

A friend of mine has a third-generation Apple TV, running the latest version of iOS.

His Apple ID is an @gmail.com address, which he's signed into his Apple TV with, under the iTunes Store heading.

The problem is, when he goes to Photo Stream on the home screen, his Photo Stream and Shared Photo Streams are completely empty/blank. The reason being that he isn't signed into iCloud, since the Apple TV doesn't have a Settings > iCloud page to sign in on.

Any suggestions?