Bigger Giants, Terrorgheists and Arachnarok Spider
Every play Skyrim with the mod for “Giant Giants”? This is basically that, only it also extends to the Greenskins' gigantic spider unit and the Vampire Counts' big evil bats. Watching giants stomp into enemies who are now no larger than their toes makes them even more frightening.
Chaos Steeds Resized
While we're embiggening things, let's make those Chaos Steeds bigger as well. According to the official background, Chaos Knights ride mutant horses who have been altered by the power of the warp to be terrifying beasts with red eyes and fangs, so it's only right they look larger than ponies.
Resized Lords and Heroes
Let's not get carried away making everything bigger, though. The special characters who will be leading your armies are already super-sized to make them easier to spot on the battlefield, which is a bit odd when some of them are regular people who just happen to be wizards. This mod shrinks them all down to the same scale as the units.
Forest Cosmetics and Varied Trees
One downside to Realm of the Wood Elves is that its units look quite samey. The variations between Elves are so minor it's like they're retail employees allowed to add only two items of flair to their uniform. Forest Cosmetics tweaks the colour scheme, including more hair colors, while Varied Trees changes the bark of Dryads and Treemen so that they look pleasantly seasonal.
The berserk, shaven-headed and suicidal Dwarf Slayers look a bit uniform in the base game. With this mod some of your Slayers will be charging toward the enemy wearing battle kilts, which are far more stylish than any armor you care to name.
Varied Zombies and Dirty Zombies
If you're disappointed that every random corpse you dig out of the grave to add to your army of the dead looks much like the last one then these mods should help. The first adds new Zombies who carry different weapons and look more like the soldiers of the Empire you'll be resurrecting, and makes their outfits a bit more colorful as well. The second makes the undead more rotten and grotesque, and there's a version that's compatible with Varied Zombies too so you can have both.
Beastmen Color Variations
Even if you're not playing as the Beastmen thanks to the DLC you'll probably face them a couple of times in the campaign. Beastmen Color Variations makes them look a bit less drab, although a bug means sometimes they turn white or gain splashes of red paint when you pause the game.
Mousillon City of the Damned Vampire Counts Subfaction
While the three main factions of Vampire Counts have homes in the eastern Empire, there's a fourth group beyond the Grey Mountains who start in the city of Mousillon. Being based out of Bretonnia, it would make sense for their soldiers to resemble the Bretonnian armies and this mod Frenches them right up. You might have some conflicts with other Vampire mods, like the Human Levies, however.
Men of the Empire
In the 8th edition of tabletop Warhammer Imperial state troops were given some more heavy-duty armor to march off to their deaths in, and the Men of the Empire mod makes them more closely resemble those miniatures. There's also a version that removes their floppy hats, if you're some kind of monster who hates having soldiers who look like they're also artists from the Renaissance.