I recently got a hold of the Chaos Chosen from the Dark Vengeance box. There is a lot of nice details in the models but I wanted to try modifying all of the models in some way, starting with the Chosen with the power maul. I thought the model had a cool helmet but too bad he's carrying it instead of wearing it.
Snipped off the head, put the helmet in place and filled the gap with Greenstuff.
The model with the lightning claws was probably my least favorite of the chosen due to his pose. He just didn't seem very threatening. So I removed the lightning claws and dug out the severed heads from my spare bits box. I think the part came from a Skaven set. The other arm will have a large Chaos Fantasy ax that I found.