Facebook has finally roll out the the feature that lets you edit your Look Back Video, I am not too sure whether the feature has been rolled out to all users. Here is the direct link: https://www.facebook.com/lookback/edit/.
You will be able to choose a fix number of photos from the four categories of the Look Back video, namely:
- Your First Moments – 3 Photos
- Your Most Liked Posts – 4 Photos
- Uploaded Photos – 9 Photos
- Photo Grids – 37 photos