I downloaded The Ultimate Evil's mask and added it in game, unfortunately all it showed was the structure (I think you guys call it the mesh) but the skin did not show up, all that appeared were white and black stuffs.
That means it's missing some texture files.
First of all, it should have a folder in the Skin folder that says "standard", so make sure it has that. If it doesn't, rename the folder in there into standard.
Now if that doesn't fix it, make sure each component has a reflection and glow file.
For example: male_basic, male_basic_glow, male_basic_refl... or extras, extras_glow, extras_refl. (Portrait does not use a _glow or _refl file)
Hope that helps ya.