I have been working on the main central piece which is a giant rock formation with a big glowing crystal stuck in the centre. Above is the low poly crystal which I baked using Mike's Autobaker to save me some time. I then combined all the cavity, ambient occlusion, gradient etc. to get the final result. A lot of the material definition will be done in engine with shaders.
Here is a portion of the rock I sculpted to hold the crystal, the idea is that this will float somewhere in the centre with the crystal on top, there are also smaller rocks which will float next to this as well. Done in a similar way to above (baked on the left) retopologising these takes a long time.
Here are some shots of the crystal in Engine on top of the rocks. This is using an interior mesh to give a cloudiness inside the crystal itself, this is one of the most complicated materials I have tried to replicate as its so multi layered, still some tweaking to do but happy for now. It was also suggested by Ant that I have an Orrey in the centre with Spinning planets galaxies and stars, I really liked this idea so have started to work on this.