To create the pictures, I've just got to make a picture up where each section is a unique color. My page creator will create an icon broken up with seperate icon states for each uniquely colored section. If anyone wants to make any, feel free to link them and I'll see about adding them in. :) There probably shouldn't be too many seperate pieces though. The more pieces, the bigger the memory footprint and the slower the picture loads.
I've been working on some internals to try and improve memory usage and load time. I noticed when I loaded the geometric pattern for the first time, and started coloring it, DS's memory footprint increased to over 230MB! I changed a bunch of internal stuff and got it knocked down to under 50MB. Still too high, but improving. It also takes quite a while to load the images, seemingly longer than I remember it taking before. No idea why that is yet, though creating hundreds of objs and icons all at one time might have something to do with it. :P
If it's faster in 3.5 and slower in 4.0, you can't help it much since that's the new icon format. But if both are slow, perhaps it is something on your end.