There are so much excellent freeware generator aveleble, my advice; play and understand them, you'll have months of pleasure and you'll learn fractal with them after may be you'll buy a commercial generator. To start try Fractalvizion, Cold_IFS, Tierazon 2.8 or 2.9, FractalExplorer, Sterlingware, Vchira, ChaoPro and many other I put them in order of ease to use in my opinion.