Really take a look at pidjy's galleries. He has doen soem impressive work using that technique. Original moron has a number of nice greebles and at sci fi meshes Ozylot has a bunch made in wings. A number of approaches you can use. The terrain one is works well but is a bit different from normal modeling. Otherwise you can make small greebles in another app and import them use a modular system like Ozylot or original morons work. then you can get a lto of milage out of it. There is also the pure texture route too.

The wit of a misplaced ex-patriot.
I cheated on my metaphysics exam by looking into the soul of the person next to me.