ayg wrote:

It's not possible in the software without some kind of custom script. Get an adminbot to do it, perhaps.

Well, in fact it is possible:
$wgLogo = "Wiki-" . date("M") . ".png"; To have from Wiki-Jan.png to Wiki-Dec.png

Having it uploaded by Mediawiki makes it only slightly more complicated:
$hash = md5($wgLogo);
$wgLogo = "http://upload.wikimedia.org/wikipedia/nds-nl/" . substr($hash, 0, 1) . "/" . substr($hash, 0, 2) . "/" . $wgLogo;

servien wrote:

Hi thanks for the comments. Could you give a description of what should be done to get this up and running? Servien

Convince someone with shell access to add the above code to nds-nl LocalSettings

servien wrote:

Okay. So should I upload the logos "Wiki-Jan.png, Wiki-Feb.png..." etc. on the nds-nl-wiki and protect them (and most important to know is should the abbreviations for the month be the English abbreviations Jan, Feb, Mar, Apr, Jun, Jul, Aug, Sep, Oct, Nov, Dec?)

Servien

jeluf wrote:

This will not work with the system that we use for configuration of our wikifarm and will not refresh caches - you'd have lots of different logos due to page caching.

Please use a bot instead.

It can be done with JavaScript. See http://es.wikipedia.org/wiki/Usuario:Platonides/logoRotate.js for an example.

servien wrote:

Thanks for the tip! :D