Which options can you pass as the third parameter of Mage::run()?

[AlfonzoFaruk]

Magento is started by running \[code\]Mage::run()\[/code\] in index.php. \[code\]Mage::run\[/code\] has three parameters: $code, $type, and $options. The first two are well-documented but I can't find anything about the third: $options. I did read somewhere that you can move your \[code\]etc\[/code\] directory to another place, but what other options can I set? I hope I can set the theme package; that's what I have been looking for.