Cleo,
The current terrain generator is pretty simple. It only generates one "island", by picking 1 high spot (moutain peak) based on the screen width and height. If you want to get more variation, you can look at this line, "voronoiBehavior.addIsland(x,y,1,0.996);" The parameters are where to put the peak, what the max height is (always 1, so ignore changing this parameter) and how fast to drop off the height on the next iteration (lower number faster drop off). If you want to play around with those parameters, you should see different results. You could also try calling the function multiple times - like this.
voronoiBehavior.addIsland(0,0,1,0.990);
voronoiBehavior.addIsland(200,200,1,0.995);
voronoiBehavior.fillPolygonByHeight();
This should give you two different peaks, but I can't guarentee the results as I didn't test it this way much The current plan is to continue improving the terrain generator, so you could just wait until it is in better shape.
If you need to do some generation for a project now, follow the links in the blog, they should take you to a couple of completed terrain generators. One even allows you to export the terrain image as tiles (I think).
cheers - Shri