Loop one holds whatever you take: a video loops, a still stays.
Loop all runs the playlist in order and repeats. A video plays to its end; a still holds for the number of seconds set in Settings, ten unless you say otherwise.
Once plays through and holds the last frame.
An entry can override the mode for itself under This file, so one still can hold for a minute in a playlist that otherwise moves every ten seconds.
A file that will not decode is skipped rather than stopping the room, so one bad export cannot freeze an unattended space. If nothing in the playlist plays, the wall goes black instead of spinning.