create a flame in whatever product you like a 3d program,
after effects. put it in flash for compression, export the video as
a swf file, use the swf as an animated texture. Requires code for
the animation to play when its a texture.
You can use a png of the fire or whatever you choose for the
png in one channel, swf in another. Keep in mind in director
you can put 8 textures on an object layered or however you want to
do it. Use 3dpi this will save you a lot of time