Contrary to popular belief... 10.5 IS themeable, it's just done through custom installers at the moment, which is about to change shortly with several software packages being heavily developed. My screenshot above is a combination of the iLeopard 2.1 theme and a custom HUD "About this Mac" / force quit applications dialog hack. They can be found at the following links:
iLeopard:
http://www.ileopard2.co.cc
About dialog HUD (download the installer instead of the resource package, it's easy and accomplishes the same thing):
http://www.macthemes2.net/forum/viewtopic.php?id=16783903
Enjoy!