By simply using the program itself, you are unlikely to run into copyright trouble. The developer of the program has a copyright in the program, but not the original work that you create using the program. For example, a designer that creates an image using Photoshop does not owe Adobe copyright royalties on that image.
Instead, the real issue is the terms and conditions provided by the program's developer. It may prohibit you from using the program in commercial works. In that case, you may be breaching the agreement set out in the terms and conditions.
The tougher question is whether, in using the default parameters of a fractal program, you're violating the copyright of the programmer. I think it's unlikely that the initial parameters of the fractal program can be protected under copyright in the first place. You generally cannot get copyright protection for "ideas, program logic, algorithms, systems, methods, concepts, or layouts." It's also unlikely that a game, which uses default parameters to create new images would violate the copyright in any event. Still, I'm not aware of any case deciding this issue, so it's impossible to say with certainty.
