artrager and tsquare: its great to see that you guys show so much interest in the thread. Indeed, the function editor is powerful and it massively extends Vues scope. Of course it takes some time to get into it, but once you have gotten to the point where you have a certain control over the nodes and the function as a whole, things are getting very exciting. Especially when you are able to create a function from scratch, you can use the experience you have gained to get the look and feel that you want to achieve.

As for rocks, indeed it seems that using simple basic geometries and then further refine the geometry by using displacement  seems to offer more flexibility and power than using complex imported objects. Also, this way you can, at any stage, change the geometry completely. Another powerful option is, as Monsoon mentioned, to make parts of the coloring dependent on the displacement function. This is easy to achieve, because both, the displacement function and the color function are present in the same window and you can link any part of the displacement function to any input of the color function.

But we also have to be aware that displacement as such has not always been so clean as it is now with the latest version of Vue 8. I remember, when I experimented with Vue 7 using displacement, I was often disappointed because I could not get rid of some artifacts. Artifacts can still be produced, even with the latest version of Vue, but they can be avoided rather easily by using simple underlying geometries and by avoiding exaggerated displacement. Also one should be careful when using nodes with sudden value changes (for example "Flat Pattern" nodes).

I understand that a lot needs to be learned and I do not think that there enough tutorials around to cover all possible aspects of the function editor (the possibilities are staggering). So IMO what`s important is to have a good  understanding of the basics (no need to be a mathematician though). 
A good way to learn (once you have understood the basics) is to analyse some of the existing functions.

Once you know what the basic options are you can explore things on your own. It`s a constant learning process.

And of course it`s always good to discuss certain aspects (I think that this thread is beneficial for all participants/readers).

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