Light Spots On Blue Ice
The guiding idea is something like 'a large body of semi-opaque ice with light spots shining upon it'. If you insist on a rationale then it could be 'wheezy - penguins - antarctica - ice', but in truth i was not really following the 'themed theme' idea.
There's a version with the Debian logo in its traditional colors and a monochrome one, and also the original attempt in light blue, but that one does not go so well with GNOME. Consider the dark one with the red logo as default.
Also, i made screenshots with GNOME and KDE at their current state in testing, i assume this is more or less what they will look like in the release.
2012-03-25: changed the font in the logo. This may be temporary, here's why. Also uploaded said DFSG-compliant logo.
2012-06-22: Changed Colors and Contrast. Picked the version with the monochrome logo and removed the others.