An extra option on each page (hourly basis, daily basis, cronjobs) where you can activate random messages.
You can then add as many messages as you want (with a limit somewhere, of course) and the bot will not send a specific message at the specified time, but will select one at random.
This could be useful, for example, for servers who want to send a different (random) message every morning in the chat to increase activity (always the same message is also a bit boring in the long run).