I was playing with my filters in PSP when I discovered this effect. It almost looks like silk.

For this tutorial you'll need :

PSP7
A gradient of your choice
KTP7 Fluid
20/20

Let's get started. Open a transparant image 200 x 200 pixels. Floodfill it with your gradient.

Apply your filter KPT Fluid, click on the little button (see screenshot below)

Select this preset and click ok.

Apply your 20/20 to make your tile seamless and you are finished !!

Here is another result.

I hope you enjoyed this tutorial :)