You have to inable "Photo Stream" in iPhoto and add the pictures to the Photo Stream to be able to see them on the Apple TV under the Photo Stream. I don't know if this is a requirement but I had to have my iPhoto active the first time before I could see my pictures.
I've gone to iTunes>File>Home Sharing> and choose photos to see on Apple TV but still only 47 photos show up on Apple TV. iTunes says I should be seeing 1899 photos. I've also reset my Apple TV and started from scratch but it didn't change my photos or add. Any ideas?