I find that taking the time to base miniatures well, not only brings an army together but can also really make individual models stand out.
If you look at this army by DMS you'll see that the bases are all well done in the same style which really unifies the force. You'll also notice that the heroes and captains have white flowers on the base. This is only a subtle addition but it really makes the models stand out. He's also done some freehand patterns on the hero's cloaks which adds to the model's uniqueness.
I did try to make each orc a character, easily picked out in a line up of hoodlums, so that helps the cause there. With my morannon orcs, I used the GW scheme and converted 36/48 so far, but the army could easily be passed by even with so many conversions. I still have many orcs and morannons to do and will still convert, but I do plan to make a very cohesive (same color scheme) mordor orc warband and I plan to make an alternate morannon scheme as well, so when I get to those in a few years time perhaps I will know better how to respond to this topic.
), I think red and gold Easterlings are a good example of this.