Cheap" way of creating variety in models

Let's say I needed a bunch (100 for this example) character models for a game. I want to stress that the models don't need to be highly detailed, if they look decent that will be just fine.

How would an artist or programmer go about creating some variety in how they look from a cost perspective? Would the artist need to create 100 different skins (assuming we can use the same skeleton) with each having a different look? Or what if items were made such as hats, helmets, different colors shirts, etc and they were mounted to the model to give each a slightly distinct look?

Or is there another way? What I'm asking is, if a game called for a few hundred game characters and the designer wanted them all to look somewhat unique is there a "cheap" way to make that happen or does it all come down to making different skins?