Here's a thread about candle flicker.
After some hours of thinking, simulating and programming, I could reproduce the statistical behaviour described in the links there in 140 bytes (uhm, sorry for showing-off, but I am a bit proud about that). I also integrated it into my RGBW firmware, adding some red&green for a warmer tint. Quite nice, used it a few times. Brighter than a real candle though (a real candle has about 12 lm).
However these candle flicker modes are unrealistic in one respect: Inside a room (no draft) most candles I had just burned very steady most of the time, i.e. no flicker at all.