This little creature overhaul is one of my older works. It is so old that I can not remember what exactly was changed, sorry.
All I know is, I like it a lot.
This is just a replacer for a few vanilla creatures, so be careful what you overwrite. Make backups!

Skeleton: Has glowing eyeballs and a spooky bluish glow.
Wraith: Is more transparent and has chilling idle sounds.
Ghost: More transparent. For transparent creatures I can not remember if it was only texture or also mesh that was edited, so I packed both.
will-o'-the-wisp: slight color change.

I also added better corpse textures, that make corpses look more "fresh". The textures are separated from the zombie textures and therefor include the meshes as well.