I recently painted up this Iron Warriors Daemon Prince as part of a commission.  I decided that I really wanted to add a little flair to the mini as a whole- so to make it stand out on the battlefield he has a nice customized base.

The base is simply green stuff over a normal base.  Carving a chaos star into it is simple enough.  After that, I painted it exactly the same as I have with lava cracks (including the Object Source Lighting from the ground).

The conversion is partly my work, and partly the work of my client.  The mask was taken from a Defiler, while the hammer hand comes from the Cygnar plastic warjack kit (Warmachine).  Altogether, I think he achieves the half mechanical look needed for the Iron Warriors.

Anyway, enough talk:

chaos-marine

chaos-marine-2

chaos-marine-3