For the Halloween games.. I have used a free 3D object of a pumpkin and rendered it against a background created with the Nature Scripts. You should watch Michael Hobbs great introduction to using 3D objects in JWildfire in a video tutorial here.
There are so many free .obj files on the internet to experiment with and they can really bring out the depth and variety of fractal images you can create.
In the Zip file you'll find the flames to create the image, but you'll need to add the 3D obj file via the gear icon on the obj_mesh_wf variation.