First of all, it's great you figured out what type of army for Chaos you're going with. Khorne is pretty simple too follow in terms of design and color: War, blood, red, axes, skulls, trophy taking, berserkers, no magical units, brutes, strong, Gladiator kings, and Scarred.
When you build your Khorne army you should consider a good color scheme, either one that exists or one of your own. The more fearsome are the World Eaters, the progenitors of the Blood God. Though they are mostly scattered and divided they have no trouble uniting to spill blood for Khorne.
The key Colors you should consider when painting are: Red, Bronze and Black. These are the main themes for any Khornate.
When Designing/Building your units you should consider if they have any trophies. Specifically skulls, to add to the skull throne or too show off as a prize. This is VERY important for a Khorne Lord, as he must have the apperance of a dominating gladiator king. From his bloody weapons, his scared face and armor and finally his prized offerings to Khorne.
One feature that marks all Khornates are the implants of the World Eater Primarch Angron, the Butcher's Nails. These drive any warrior into a bloody killing frenzy.
Khornates are not elegant as a Slaaneshy follower or a plague bloated child of Nurgle. So their weapons will show several signs of scaring.
Likewise, Khornates do not employ Psyckers in their ranks, neither as a Daemon Prince. So there are no sorcerers or spells for them too use.
When it comes to combat, Khornates favor melee combat, preferable with an axe.
Khorne Berzerkers are an ideal choice for an army starter. With the new rules they can be used as regular infantry if following a Khorne Lord or the Hero Kharne the Betrayer.
I guess that's all I can offer you. Also, you can check out the painter site:
http://www.bolterandchainsword.com/csmp.php for roughing out a color scheme for your army before painting.