This is an implementation of the tutorial "Replace Elgg favicon icon" (http://www.perjensen-online.dk/12/replace-elgg-favicon-icon/). I am uploading this because searching for this solution up to now leads only to three results:
With this plugin the favicon is still hardcoded (might change in future realeses - if any), but I consider it less problematic to "forge your own custom plugin" then modifiying elgg core.
To use this plugin, you have to unpack the zip file below elgg/mod as usual and replace elgg/mod/myfavicon/graphics/favicon.ico with your one. This plugin is delivered with the default elgg favicon, but to tell the difference the dot is red, not blue.
You need to provide your logo in favicon format, this plugin does not help you in converting other image formats.
Initial release. All credits go to Per Jensen.