Here's a folder of MSG presets that generate different halftone effects based on space filling Hilbert curves. You need Studio Artist 4.03 to use these particular MSG presets. These presets were posted in response to a forum discussion about a particular image i posted awhile ago.
Here's an example of one of the presets. How to build these kinds of effects will be discussed in detail on studioartist.posterous.com in the january 11 and 12 posts.