In Warhammer, there are four major Chaos gods. My favorite is Slaanesh, the youngest of the gods of Chaos. He is the god of excess, sadism, and the dichotomy of pleasure and pain. Since I had plenty of models laying around, I tried to find a way to bring them together into a cohesive army. I think it worked well with the Warhost from the City of the Six Spires.
Older Dark Elf models with some Dark Eldar bits from Warhammer 40k became my Chaos Marauders.
The Chaos Warriors from the game Battle Masters became my...uh...Chaos Warriors.
With some Warhammer 40k bits from the Chaos Space Marine range, Chaos spawn bits, and some other random findings I created my unit of Chaos Forsaken. Although they have found recent use as a unit of Chaos Chosen recently.
My Demon princess was converted by taking an Inquisitor model, filing down the wires on her, sculpting her hair, and adding pegasus wings. I still haven't gone back and fixed her eyes, but she doesn't see a whole lot of play, so I haven't felt the need.
This is a completely converted Hell-Cannon. This took a long time to fit together and sculpt. I still am not entirely happy with all the flesh color.
The guy on the left holding the banner is awesome. I am very proud of the Chaos star/eclipse on his banner.