Here is one of my Night Lord that was made back in 2006, I recently went back and decided to give him an upgrade.
The most annoying part was giving him his new face. I had a lot of trouble cutting the metal head and then combining it with one of the newer Chaos Marine heads. To improve his pose, I exchanged his left arm with one with a chainsword. At some point when I was first started using greenstuff I had added little bat wings onto his leg, I've improved a lot since then and so, I redid the wings. The last thing I did was give him a new customized base. Now all he needs is a new paint job.