The statue of Talos has him pointing a sword down at a serpent...
Are they enemies in any of the other games? Or is there some lore for why they arent in the game?

Tsaesci?

Ohhh. They seem pretty cool from what I'm reading on the wikia.

A shame they probably won't be in DLC because it says they're on a different continent though :\

Tsaesci are the serpent-folk of Akaviri to the east of Tamriel.
As for enemies, there has been medusa and lamia creatures you battled in Arena and Daggerfall.

There are sort of lizard like critters in other games (Guar for instance) but I have not seen snakes in any of the games so far

Dragons, technically, are serpents.

There's one really really big serpent that everyone is trapped inside. That one just keeps eating its own tail. I do believe that's the serpent that Talos is driving his sword into.