[peterska2]

The board offline message is a standard error message page which uses the text from the vboptions text box. AFAIK this is in every single php file and so changing it, while be very time consuming to do would all be code modifications and therefore wiped out at every upgrade. Changing the standard error message template would change it everywhere that it appears and it is used in a lot of messages that come up in various places throughout the site on a regular basis so this is not practical.

However, you can use HTML in the board offline message box in your vboptions, so you could make some minor changes there. It would still display as the same style of page but you can add images or other effects inside the box which contains the message.