Yeah, you can do that.
First, draw your pattern. Think in terms of tiles, just like you would for a bitmap pattern. If you want to include blank space, use an invisible square as a frame.
F5 to bring up the brushes window, and click on the Swatches tab.
Select the pattern you drew, and drag into the little Swatches window.
That's it. Draw a circle or something, select it, and try clicking on the pattern you just created in the Swatches window. It should be painted with your pattern if all went well.
One drawback to using patterns this way: they can look a little too regular and computery if you don't later expand them and shift them around. You may want to make a few slightly skewed variations to get more of a Zipatone feel.