For this last experiment for 2013, I used the Circle effect and CC Griddler with Curves for contrast and CC Composite, Levels and Gradient Ramp for colour. CC Griddler is great for creating all kinds backgrounds, especially when duplicated. In this example I used three copies for an increasingly smaller, dot-like appearance.
Here’s my project file. What can you create? Take 30 minutes and see what you can come up with, then post a JPG in the comments.