Models, price and rules are probably the among the most "need" to be done on the Tomb Kings. I'm fairly new to Warhammer, and I will be picking up both 40K and Fantasy, when going through the list I was absolutely stunned by the beauty within the Tomb Kings. I agree with Sphinx and Obelisk, other than that, I have found them to be the most equipped to handle anything and the most formidable as a foe.
So what does the Tomb King need? Save for the big three listed, I personally would like to see more of the background of the Tomb Kings, perhaps a novel or two, I haven't found one yet, so if there is one lemme know, other than that I am in agreement with the big three.