Hey, saw your post in the blog, thought I'd give you some thoughts on that (I used to play chaos.)
First off, I think chaos terminators are far superior to normal termies. For one, their guns are actually twin linked bolters, as opposed to storm bolters that normal termies carry. Though they don't get two shots from 24 inches, but they are twin linked and rapid fire. Next, they get normal power weapons as opposed to having power fists stock. This is good because it lets your thin out the ranks of termies before their power fists get the chance to attack you. And, for the same price as a normal termie (40 points) you can have your chaos termie as a champion (3 attacks, and everyone in the squad can be upgraded this way.) This will help you wipe out a termie squad before they even have a chance to fight back.
Chaos rhinos are also pretty useful (seeing as how oceanic eldar cant kill them :) Seeing as how 5th ed is all about mech, chaos rhinos can fill their role as transports well because of demonic possession. While it is 20 points, it lets you fearlessly charge your rhino across the board and into your opponents face (so what if it lowers your BS to 3, not like your supposed to be shooting with a transport much anyways.)
Defilers are also amazing. I would recommend two. This way if one gets shot to hell you still have another. The battle cannon seems like the most useful weapon on a defiler, but most people aren't aware of its prowess in close combat. If you get one, give it all close combat weapons, and charge it (or use the battle cannon if it still has it) and use fleet to get into the opponents face. Defilers are probably the most fun heavy support choice in the chaos list.
If you plan on giving your regular marines a mark, the one that I recommend is mark of tzeentch. A 5+ invuln certaintly helps them capture objectives. Slaanesh is also really useful against regular marines as you can attack before they do and hopefully wipe them out. Mark of chaos glory also helps in case you lose combat and need to make a reroll for moral. (Dont forget a termie squad can deep strike and not scatter within 6 inches of a mark)
Finally, I would recommend taking at least one squad of berserkers in a land raider. This allows you to rush your berserkers into combat and then assault out of their transport. Possessed also fill this role fairly well, but a pricey value.
Hope this helps, I got a couple more ideas but let me know what you think. Oh and the eldar army turned out great :)