It was basically a set of concentric annular segments. I originally suggested a macro in either GIMP or an office product. Rather than just recommend and run I thought I'd actually put my money here my mouth is and have a go at it. As it turns out, neither of those actually appealed to a quick and dirty solution late at night, so I went with generating an SVG image directly from python.
Those more familiar with using script-fu or the Libre-Office scripting tools could probably integrate this into one of those (and please feel free to us my code to do so) fairly quickly.
Here's a sample result, exported to png:
For a colourless, scalable version try this link. Blogger wont insert an svg as an inline image, but you can save it to your machine and convert it to whatever format you like.
You can get the source code here. It was thrown together very quickly, so it's far from perfect, but it should be commented well enough to make basic changes very straightforward. I've only tested it on my Ubuntu machine, but it should work on any python install, with the addition of the svgwrite package.
Edit: I created a libre office drawing with this as a background, and rotated text objects, for (reasonably) easy editing. The odt file is in a shared google drive folder.
If anything is missing, inaccessible, or unclear, let me know. Preferably on Google+, but a message here is OK too!