There are two tricky, and often time-consuming, steps to making a more complex (and somewhat organic) patterned paver Floor family. First, if you want the pavers to render correctly, you need a high quality image for the material asset. Then, you need a corresponding hatch pattern for the basic graphics.
For the image, I will often do an image search to try and find a suitable image that I can use or Photoshop accordingly. While searching I discovered that Belgard, a paver (and other hardscape) manufacturer, has many paver images available online (if you know where to look). They even have the same pattern in various colors, though the colors do not seem to always match the available colors on the website…
So here are Paver families for the Eco Dublin, Old World, and Urbana Stone pavers.
If you want to use the images, here are the ones I found (you will have to download and reload them into the material asset from a known location):
landarchBIM 
Have you tried the tile-based texture editor inside Revit? You can get some pretty good results for ‘realistic’ mode.
Hm, yes I have used it some. Though I should probably look at it more thoroughly. It certainly would be a good way to create more regular pavers.