A while ago on my Brush Port Blog I posted a 2-part article on the subject of creativity and inspiration. Although aimed more at the concept artist, in part 2 of the article, there are links to a collection of custom Painter resources which you may care to download.
Of particular note is a technique I stumbled upon for controlling the twisting movement/ frequency of a custom loaded palette knife variant (Lumi Twist LP Knife) by changing the scale value of the current pattern (via the Patterns palette). This method in combination with the custom Pattern resources can also produce some very graceful flowing ribbons;

The image below demonstrates the effect of changing the Pattern scale value on the brush stroke produced. For the stroke on the left, the pattern scale of the custom Checkerspots pattern was set to 50%, whilst a value of 200% was used for the right hand brush stroke.
For the technically minded, the stroke Angle is set to Source for the Lumi Twist LP Knife, which means that as the luminosity of the source (defaults to current pattern) changes, then so does the angle of the brush stroke. Generally speaking, increasing the scale of the pattern has the effect of making the changes in luminosity further apart, therefore the twists in the brush stoke also become further apart.

Below are the links to my original blog posts (the custom resources can be downloaded from part 2);
Creativity and Inspiration Part 1
Creativity and Inspiration Part 2