Hi jake, yeah that kind of rock structure is not a good fit with the NURBS modeling techniques that MoI is based on which are more about building surfaces from profile curves rather than making randomized rocky looking things.
You will probably want to look at displacement mapping in a rendering program or ZBrush like others mention above for making something really lumpy and bumpy all over like that.
That kind of project is just not a good fit with the modeling techniques that MoI uses. There are a variety of different 3D programs that use different methods for construction and something like that is a better fit for a different program.
If you had something that was a little more "stylized" in nature, there is a new tool in v3 called flow which is able to map a 2D object onto a 3D non-planar surface, see here for some more information on that: