The Time Slice app allows you to simply turn a video into a single photo by slicing frames of the video up and putting them back together again in a single photo.
This app works extremely well with time-lapse videos. Especially time-lapse videos that show the sky going from day to night or night to day. It has never been so easy to capture the transition from light to dark (or vice-versa) in a single image.
Have fun and be creative!