The main initial way that people excited by Numberscope's possibilities want to extend it is by creating their own Visualizer. Sometimes this addition is to tweak the behavior or add a feature to an existing Visualizer, or sometimes it's a whole new idea on how to look at the universe of numbers. Whichever is the case for you, this guide will show you how to go about implementing a new Visualizer.
Currently in order to do this, you must begin by setting up to run Numberscope from source code on your own machine. (Rather than the public server -- hopefully in the future Numberscope will switch to an architecture in which you only need to have the code for your visualizer locally.) You also may want to get set up with a convenient code editor for working with the program you're going to create.
Once you have that working, you just need to add one code file to calculate and display the images you want to create. Once that file is in the correct place, you simply restart Numberscope and your visualizer will appear as one of the options.
The details of these two main steps are on the following pages. If your visualizer ends up working well and you'd like to submit it back to the Numberscope project for possible inclusion on the public server, that's one of the topics in the Contributing section.