I've been playing with a formula combination that lxh posted with a piece at Fractal Forums. If you haven't checked out his work, you really need to, he's done some stunning work. The formula combination he used is
Amazing Surf / _RotatedFolding / _FoldingTetra3d / _addC and you can check out some of his images here [link]
I spent three long hard days just finding a sweet spot I liked to start working with.