zimbra 7.1.3 ZCS opensource (we are non-profit with zero money as in 0 )

I need an area in zimbra (in the mainwindow and as bonus in the login-window too) where I can present information to my users that will stay there so they see it all the time. Preferable I would show a few lines of html-text, but a image banner would do it also. (would add the extra work to convert text to image before)

So I was thinking what is the best way to implement something like that:

There is the possibility of ad-banners, but seems that I need to buy a zimlet there.

And there is the possibility of changing themes or skins.

I was reading files.zimbra.com/docs/skins/Themes.html and even a bit around about templates and ads but it sound complicated and before I dig into it I want to ask if this is actually the right way and if there is a simple solution or knowledge already out there that I can use without needing to build my own skin only to show cutomized text to my users.

thnx
p


ps: This is all for important changes to our system that I need to present my users this way cause them ***** dont read my emails and especially as we have a double-setup where one zimbra is kind of backup for another and users on the backup-server should always have the message that this is the backupserver and that all changes will be overwritten from the mainserver at midnight. They tend to forget that. And I cant even blame them cause they are volunteers like I am. Not getting paid (even paying themselfes for infrastructure) and therefore they dont want to waste time with just another IT-thingy. So I want to put it where they dont waste time to read it and cannot skip it