You can add a text message, either static or moving like ours is atm, You can add bbc tags to achieve this. For example what we have at the top of this one is,
[move][b][color=red]Please don't ask for support in this shoutbox, start a topic in the forum, thank you.[/color][/b][/move]
Which gives the message you see.
To get to the shoutbox settings,
Tinyportal > TPShout > Settings > "Place a fixed message or announcement at the top of the shoutbox (BBC allowed):"
Hope this helps.