NSLog();

Wow. I didn't know that desktop icons could be captured with the spacebar trick after hitting cmd-shift-4. They're not only captured, they're captured with full transparency. That's pretty nifty!

I found this information when reading about StyledWindow at bithaus. Then I used it to capture one of the icons on my desktop. I assure you the background was quite busy - not white. Go ahead and give it a try.

P.S. It's rather pointless to capture your dock, as you just get a grey bar with triangles. And, for some reason, dock icons captured in this method are also rather ugly and aliased.