Try replacing Human with a better more classical Undead if you don't have an idea for Human's replacement. When I say classical, I mean by not GHOULS as primary unit. Geez, a ghoul is supposed to be some sort of boogeyman! Here's a table I whipped up for units:
Ghoul>Zombie
Crypt Fiend>Vampire
Gargoyle>Malevolent Spirit
Meat Wagon>Carrion Cow (TAKEN FROM TIME SPLITTERS: FUTURE PERFECT

)
Abomination>Abomination is good, keep
Obsidian Statue>Oblivion... as in take the stupid statue out.
Necromancer>It's good, keep (Raise Lesser Zombies instead of Skeletons)
Banshee>Skeleton Commander (THIS guy gets raise skeleton)
That's about it.
Oh yeah, I like the skin, bit too purple in my opinion though. If you want gloom, grey and really dark grey is the way to go.