The issue is that “Photos” do not show up on the Apple TV under “My Computer”, I see it too consistently.  What I found that fixes it temporarily, is this:

1. In iTunes, go to “File->Home Sharing->Choose Photos to Share with Apple TV…”  (That is the name on iTunes 12.3.1)

2. Then turn on or off an album. (It did this for the Apple TV 2, 3 and the new ATV 4).

3. Then hit Apply and close that window.

4. Then it starts showing up on the Apple TV.

So, every time I restart iTunes, I go in there and just have an album that I don’t care about and turn it on if it was off, and off if it was on.

This has helped some people who didn’t get it fixed by rebooting everything etc.