An actual 3d fractal flame, hovering over an ocean. It's actually a composite of 3 renders, one of the 3d fractal, one of an ocean at the same angle, and a 2d version of the fractal used to cast reflections in the water.
This image rendered for three days on 4 computers before crashing, and losing all the work. I rendered again at wallpaper sizes only, just to get it online. I may never try rendering a commercial version of this one again.