I ended up using slight variations of the base texture for each chunk, painting and adjusting the texture where the roots are located. I also extracted specular maps from the final bases by simply de-saturating and adjusting the levels.
Back in 3dsmax, I made a generic dirt/rock material that I would instance for each chunk. Below is a test render of the material and its settings:
Creating the Bomb
The bomb started out as a simple sphere and then I used basic polygonal modeling techniques such as extruding, insetting, beveling, renderable splines and turbosmooth to finish it. Once again pelt mapping was used for each element which worked out perfect. Below is a breakdown of the creation of the bomb.
Shading the bomb was a little more involved than the cave and required several mixed Brazil Advanced Materials with glossy reflections, mostly using Falloff. My goal was to create a surface that still had some shine to it, but had a layer of dust/dirt along with a substantial amount of rust. To aid in reflections, I used an HDR panoramic I photographed from a probe and compiled using HDRshop. Below you can see the material network and a sphere with the material applied, along with the textures used.