We've all been there before. You're walking down the street in a big open-world game like Skyrim, and you see some plain-arse looking dude. A guard or something. You turn a corner and see... that guy again? OK so maybe he has a twin. But then you see yet another. So much for immersion.
Diverse Skyrim is a mod that tries to solve this problem. Here's the description:
"Sometimes I feel like I'm slashing and shooting my way through the same enemies all the time. Almost every Vampire is an Elf, is J'zargo really the only magically gifted Kitty in Skyrim, and what happened to that Dark Elf on his way to Solitude to join up with the Legion?"
"[This mod] adds over one hundred new NPCs with unique appearances to the Vanilla leveled lists for added racial diversity while staying lore friendly."
So basically, you'll encounter a much wider range of NPCs, rather than a clone army where only a few races get to be vampires and there are no orcs in the Imperial Legion. The mod does its best to remain lore-friendly, though, so it's not like you'll start seeing J'zargo's extended family everywhere (even though that's the mod I desperately want).
Here's a video of the mod in action by Brodual:
Now if only we could get this mod for basically every other open world game ever, we'd be set.