I've had my tomb kings for years and I'm still happy with red as the main colour after bone of course.
Red shields with gold trim. Looks really good when they are all ranked up. Red fronts on the chariots again with gold trim.
If it's done so it is not too bright it adds good cohesive colour to the army without being overbearing. A dull gold trim on them looks good too in my opinion. It goes well with the red and maintains that sense of regal riches the tomb kings had before they all became undead.
It's just my opinion I guess but I think it looks good, especially if it's done in a muted style and is not too bright.
It does look good, but I've seen them quite a lot and I've also been painting Word Bearers recently and really want a change from red.