This notification isn't as prompt as I would've liked, as it completely slipped my mind, but the new version of my Platinum Firefox theme has been released – now compatible with Firefox 1.5. 
Released a few weeks ago, this new version has fewer bugs, some patched-up colours, and most prominently, support for Firefox 1.5 (and all previously supported versions down to 1.0).
Even though it's at the bottom of the list, and has an appalling rating (I still suspect dishonesty), I hope somebody finds it and likes it – I've had some fun times (and some less-than-fun times) making it, and it should be enjoyed.
Dear DrBob,
why is the Platinum skin not available for the Thinderbird e-mail programme?
Kind regards,
Flip Nagler.
To be succinct: I haven't got round to making it yet. I created the Platinum theme for Firefox just because I was curious: I'm not a graphics designer (I'm actually quite rubbish with most graphics programs), and it's a real chore to make a release. I really want to get round to making a Thunderbird version of Platinum, but it requires tens of new icons, and there are more things nearer the top of my todo list than that. However, there have been quite a few requests for a Thunderbird version, so I will most likely get round to it someday, and notify everybody on my blog when I do make a release.