Len - NightCafe is free and you can collect 5 free credits every day.  Since I don't use it that often I click each day to collect those 5 credits. After a while you have plenty to try a bunch of renders.  I'm hit or miss with NightCafe, would be fun to get some users here to share ideas.  

Oh ya there was that one NightCafe fractal image that turned out cool...