I'm going to show you how I did my Duke Sliscus.
It's a pretty straight forward use of a Dark Elf Corsair with a Dark Eldar power weapon arm.
Here he is based in black:
Next I painted the outside edge and the inside of his cloak with scorched brown:
Next I drybrushed with Calthan Brown and graveyard Earth (although graveyard earth didn't make much difference):
Gave it a wash with devlin mud:
I edge highlighted the cloak with Snakebite leather and another wash of devlin mud:
Next I painted the scaled part of the cloak with Dark Angel Green:
Drybrushed with Snot green and washed with Thraka green:
Then highlighted each scale with Goblin green:
Next a few steps later, skin is done with dheneb stone and ogryn flesh wash. Blues are based with mordian blue, then highlighted with enchanted blue, washed with asurmen blue and highlighted with a mix of enchanted blue and space wolf grey. Hair was done with a base of Iyanden darksun, highlighted with golden yellow and washed with devlin mud:
Then for the armour I used a very watered down Liche purple and tryed to blend it from the centre out to the edges into the black (this is the first time I tried this technique and it's not perfect, but I'm ok with it

) Then I tried the same technique over the top with gradually lighter shades of purple, I used mixes with hormagaunt purple, bleached bone and skull white. The lightest shade was used for the edge highlight agter a wash with leviathan purple:
The final stage was the base, this is an urban style base painted with adeptus battlegrey, drybrushed with codex grey and dotted with a few different shades of brown and finally washed with devlin mud. The swords were based with Leadbelcher, washed with badab black, highlighted with chailmail, washed with thraka green (to give the impression of being coated in poison) and highlighted with chainmail again. The hilts were based with tin biz, layered with dwarf bronze and higlighted with shining gold.
Here are the final pictures:
Hope you like it and might find some of this useful.
Comments welcome!