@Scrounge  
Okay, before I forget again…
 
Ahuizotl (take 2): A wealthy and charming businessman and politician rumored to have ties to organized crime, particularly antiquities smuggling. Notable bad blood between him and bestselling author A. K. Yearling. Has a soft spot for animals, especially cats, and gives generously to animal shelters (some think this is a public image thing, but nope, he actually cares). As his home is near Canterlot High, this brings him into contact with Fluttershy more often than she’d like.
 
 
@Thegreatmewtwo  
@Roy-of-Asturia  
The tatzlwurm could also be homaged by coloring a subway train to look like it.
 
 
@Roy-of-Asturia  
The Shadowbolts already showed up as a soccer team in the IDW comics annual from last year, though I suppose they didn’t get fleshed out much.

@Roy-of-Asturia  
Tatzlworm (Tat.zl): A computer virus, classified as an Internet worm.

@Background Pony #A45D  
Allow me to add the following or barge in:
 
Gilda: Junior or Senior; delinquent; former best friend of Rainbow Dash
 
Lightning Dust: Junior; Soccer Club Representative; Rainbow Dash’s rival
 
Sombra (alternate): (Ex-)Principal/Dean of Crystal Academy, now reduced to some school for hard knocks, you know the stereotypical delinquent schools in Japanese media
 
Dr. Caballeron (if he counts): Syndicate don; think of The Cartel based in Equestria
 
The Shadowbolts (if they count): Just imagine the Black Team from Stephen Chow’s movie Shaolin Soccer
 
Suri Polomare: Senior; Fashion Club Representative
 
The Dazzlings (after the events of Rainbow Rocks): Founders of their own sorority, but still students of Canterlot High
 
Garble’s gang: Well, dogs of different breeds, just like Spike
 
Porcina (G1, if she counts): Ex-supermodel; owner of a local mirror shop
 
Mane-iac’s buddies (G4 IDW comics, if they count, >>728729): the same as @Scrounge mentioned; perhaps they will be in some sort of pro wrestling stable (no pun intended) as their gimmicks, Mane-iac herself included
 
 
I would not mind the other monsters/creatures [Please refer to >>743699]. They will be either plushies like Discord (>>656319), or real animal equivalents.  
Parasprites = Locusts; Timber Wolves = Timberwolves, naturally  
That suggestive giant sand worm (not calling it by its official name) = plush version of it
 
 
PRAISE BE TO DECEPTICON!

@Background Pony #A45D  
Mane-iac: Basically the same, still a comic book character, still fictional, but her enemies are the Power People (as calling a human superteam the Power Ponies would be kinda weird).
 
And I’ve been revising my Ahuizotl idea in my head today, but it’s late as hell so I’ll put that up tomorrow.

@Background Pony #A45D  
Ursa Major and Ursa Minor: Bears from local zoo. Some idiot kids (no prizes for guessing who) let the smaller one out.
 
Diamond Tiara and Silver Spoon: Basically the same, just on two legs instead of four..

@Background Pony #A45D  

 
Flim Flams: Local Pawnbrokers (as seen in the shorts) and enterprising, though failed, reality TV show stars.
 
Grogar: Former university professor who was infamously dismissed for his unethical occultist experimentation on the young and dead. Still continues his experiments under the guise of a well-to-do mortician.
 
Scorpan: Crime Lord Tirek’s brother and capo, except that he testified against him once before and serves a reduced prison sentence. Disappeared from the immediate area after he was paroled and released to elude Tirek and his boys.
 
Discord (building on): Stalker, prankster, and repeat escapee of a local asylum. Though he studied psychology in university with Luna and Celestia, he is wanted on numerous violations of restraining orders, though makes a mockery of authority.

@Background Pony #A45D  
Chimera: Triplets, violent bullies but will leave you alone as long as you don’t get too close.
 
Ahuizotl: Local short-story writer and used car salesman. Fond of power, money, and cats, but not likely to be actually dangerous unless Canterlot High and the surrounding area are sealed under a dome.

Here’s how I see various MLPFIM villains in Equestria Girls:
 
Chrysalis: Headmistress of the rival school Changeling Academy, who constantly seeks to lure away Canterlot High’s best and brightest
 
Discord: The class clown and school prankster
 
Sombra: The school bully who terrorized the other students prior to Sunset Shimmer before being sent away to Juvie hall after students Shining Armor and Cadance came forward and testified to the Principals.
 
Tirek: A local crime boss who employs teenagers as his henchmen.

Like a superintendent who just got out of prison for aggravated assault, battery, fraud, and 12 other petty crimes that the school board does not like to talk about.

Yeah… Tirek should look more like this guy.  

Mister T-rek?

Superintendant Tirek?

I like this design, though the eyes are a bit odd. But his original eyes would probably be even more odd.

What the fuck is wrong with his eyes?