This is easily the most ambitious sculpting I've ever attempted and I've learnt alot about doing it in the process. I'm pleased with the result, and I hope to do a decent paint job on it.
The conversion is based on a WFB Chaos Warrior, with a leg swap to give him a more power armoured look. The head is taken from the Space Marine commander box. The remainder was endless green stuff work.
Two major lessons I learnt from this project:
1- Only ever work on a small part of the model at a time, don't be tempted to do big swathes of it at once or you'll spoil what you've just done.
2- You always need less green stuff that you think you need. Some of the amounts I ended up working with on this model were minuscule.