When I was playing Warhammer Fantasy several years ago I had a Vampire Counts army. By the time I was through I had quite an impressive undead bits box. When I was digging through it a while back I found a head that just screamed chaos to me - a nice blank expression zombie head.
Once I had found the right zombie head it was time to find the proper body to put it on. I tried putting it straight on a Space Marine body but it just didn't look quite right. I thought it needed a helmet of some kind. I tried to hollow out a space marine helmet so that you could see the face poking out of it but that did not work very well.
As I was poking around my pile of space marine heads I found one that I thought would work. Instead of hollowing out the inside of the helmet I decided to take the helmet away and leave the bottom.
The end look worked out well. It almost looks like some kind of mad scientist device that keeps a head alive. When I put my next batch of Chaos Space Marines together I will be sure to stick this on one.
