Sounds like an interesting feature request. I have always made a block of rules to trigger stuff like this for a vacation, including having different times for different days so it does not look too regular. Sometimes I try to get fancy and trigger "travelling" lights from room to room.
Completely random might be tough to check though. How would you know when it is supposed to run, and you need to prevent them from coming on at unreasonable times (everything on much of the night, on during the day, etc...).