Also, what's a Wardrobe? Always puzzled me.
Wardrobe [wawr-drohb] noun
1. a stock of clothes or costumes, as of a person or of a theatrical company.

Now, with the serious answer, the wardrobe in TL2 is what makes possible por the player to wear differents armor pieces and also different skins colors, hair styles, etc.
The complete wardrobe systems is a bit complex since it has a lot of interaction parts, but once you understand it, it becomes pretty straight foward.
At a technnical level, the wardrobe makes possible to change part of one 3d model, for the parts of another. For this to be possible there are some requirements.
1- The 3d models: The 3d models for the player or monster need to have different materials defined, this different materials are the ones that can be changed for the parts of others models. This "other models" also need to have different materials defined. If you work in blender this material should all be in separate objects.
2- The Wardrobe.dat file: For the game to now what material to remove and what materials to add to the player model, you need to define the "Set" in the wardrobe file, for example a Helmet would remove the materials for the human head, and add the material for the helmet. This sets are defined in a generic way, that need that the materials for the models have an specific naming convention.
3- the item unit file: The item need to have defined in the Wardrobe tab, what set it is, this means if it's a helmet, a chest, a boot, etc. The 3d model that the player will wear when equiped. The type of player, male, female, class, etc.
4- the player unit file: The player need to have the "wardrobable" flag checked, so the game will check for the wardrobe tab in the item file, the set in the wardrobe file, and last the materials in the 3d models.