Hey, you've probably found an answer to this question by now, but I'll post from my experience to help the next asker. I was trying to load an album of baby pictures as the screensaver for my parents-in-law for a similar situation. I took the Apple TV to my house and connected it wirelessly to the network, and turned on Home Sharing so it could see the albums on my iMac. I selected the album I wanted as the screensaver, and let it load. When I brought the Apple TV back to their house, it had stored all the photos in memory. So long as they don't change the screensaver, it should keep the photos memorized (my iMac was, of course, nowhere to be found on their wireless network). You'd have to check on what the limits are for this approach, though. I don't know how many pictures it can keep in memory or for how long.