Just to throw the idea out there, CSS is really capable these days. To get a
more boring design, it may not be necessary to change much of anything
structurally if you modify the styles/classes used. One could even keep the
old (current/fancy) style available from a selection drop down like this:
http://jsfiddle.net/gyoshev/Gxpfy/ ;(could just go on the bottom of the page if
there isn't a good place to put it).
So mostly it would be changing some things like icons to use CSS rather than
images and then creating a default stylesheet based on a white background, less
gradients, boring logo, etc.
Also, one thing that you could do which is not boring but will probably
actually be appreciated by most people is to just use a non-default font from
Google Fonts (pre-downloaded ideally). Even the Rust site as boring as it is
seems to use a less common (possibly downloaded?) font.
This is just an idea.
