All brilliant ideas. I also think the Malal idea's pretty cool too. (funny thing about the symbol: A few weeks ago I was inventing a symbol for my other chaos armies; and I came up with a face that was half black, half white, a red eye, and surrounded by a chaos symbol and a circle; then I see the Malal symbol and I think to myself, god damnit).
I wonder if it would be ok to invent my own minor god (i'm not completely sure about this so don't nerdrage please). Although Malal seems pretty fun; and when people ask you what your chaos space marines are dedicated to you have something different and interesting to say.
I did hear that servants of Malal hate religion and don't live long though.
"In the embrace of great Nurgle, I am no longer afraid, for with His pestilential favour I have become that which I once most feared: Death."
-Kulvain Hestarius of the Death Guard