Its been brought up, but it wont happen. The code simple wont allow it, plus it will slow down the site.
The code for the new site have been and will be tweaked even more towards speed so adding extra code for custom themes will eventually slow down the site!

But I agree, the idea is OK!

It is down.

I go out of my way to avoid sites with white backgrounds.

If a skinning site cannot be adjusted via skins itself it should at least not have an abundance of non-colour, neither white nor black.

Shows a severe lack of creativity....and thus a poor advertisement for the site content.