The nature is a curios case of intertwined order and randomness. Silvia Cordedda pays a tribute to it with her fractal flora renders.
Both versions of Apophysis are free software for Windows, both perfectly run under WINE on Linux. There’s also a very similar native applicatuion called Qosmic, if you are interested in flame fractals, not mentioning a few plugins bundled with GIMP.
She also creates some rather jewelry looking images like these two.
You can find plenty more works by Silvia in her gallery on DeviantArt.