I recently noticed that some images in my Apple TV screen saver were appearing distorted -- incorrectly cropped, shimmery, with vertical lines through them. I spent a fair bit of time trying to figure out what the images had in common when I realized they were all black-and-white. I did a Get Info on the images and they ALL used the Color Profile "Gray Gamma 2.2". Opening the images in Adobe Photoshop Elements 10, converting their color profile to sRGB (Image > Convert Color Profile > select sRGB option), and then saving them back out eliminated the problem once I forced the Apple TV to refresh its cache of images.
Hopefully Apple will realize this problem exists and do something about it -- I am posting it here for the benefit of anyone else who may run into this problem and can't figure out how to solve it.
The very latest Apple TV software update appears to have fixed the problem. I set a folder containing nothing but Gray Gamma 2.2 images as my screen saver and they all appeared correctly.