As I create each new image, I first collect some interesting layers, then start tweaking formula parameters, adding more layers, changing merge modes and gradients, moving things around, and making lots of use of Undo and Redo. 

With each substantial change that I think might signal the optimum effect, I often render a test image, but then keep working on alternative options while the render calculates. One day in 2008, I realized that the image I was working on was generating an unusually large number of intermediary "This-might-be-a-keeper!" renders. I decided to keep them all and then stitch them together in a slideshow that demonstrates my workflow and the evolution of a finished image. It's also great proof that if I stop creating after the first several dozen (hundred?) times I think an image might be done, I would miss so many better options to come!

Here's what I mean:

I think this tweak and re-tweak process is something that every creative artist should employ. It means sacrificing instant gratification, inviting future frustration and greatly lengthening the creation process, but the results are so worth it!