instead of being a waste of space like our friendly Turbo Ski...I'll actually contribute.
This is my Mercs/Traps Mastermind - Madame Callisto
Four screenshots w/ all the pets and their individual upgrades should cover what you're asking for.
Soldiers, Spec-Ops, Commando w/out Upgrades
Soldiers, Spec-Ops and Commando w/ only the 1st Upgrade
Soldiers, Spec-Ops (oooh stealthy) and Commando w/ only the 2nd Upgrade
Soldiers, Spec-Ops and Commando w/ both Upgrades
If I wasn't saving the charges on my pet temp powers, I'd be happy to throw something up. 
perhaps ParagonWiki has a "Pets" category? for both temp powers and pets summoned via powersets?
"City of Heroes. April 27, 2004 - August 31, 2012. Obliterated not with a weapon of mass destruction, not by an all-powerful supervillain... but by a cold-hearted and cowardly corporate suck-up."
I think I can add to this, I'll have to go through my pages and screenshot collections and I'll post once I've found all my pet related pics or taken ones that I don't have.
Regarding pets, I'm assuming you're looking for mastermind pets, controller/dominator and defender pets, and the various temp power pets. But there's also pseudo pets, like lightning storm, tornado, target drone, auto turret, photon seekers, voltaic sentinel. as well as the nifty to look at but don't do anything veteran hologram pets. Are you looking for pics of all of these?
I checked pwiki's entry on pets. They have limited pictures of some of the mastermind pets, but not very many, if any pictures of controller/defender pets. Scuzzbopper's COH Codex of demo edit model names has a limited list of pet names as well, but one its limited and two there's no screenshot picture page up for them.
until then yer welcome to check my page, the Heriverse link in my sig, and browse through the pages. I know for sure that Hericane and Wherlwynd have their Singularities screenshot, and Shivans are in several. Wherrlwind's robot pets are screenie'd for reference pics, etc.
MA Arcs - #67636, #92202
deviantart page
Slag Heap: Why you hurt Guardian!? Guardian no hurt you!
I love my Fly Trap! Just don't look too close or you'll see the flies buzzing around him.
Archtype: Dominator
Powers: Plant/Thorn
Pet Name: George
I'll hug him and squeeze him and call him George!
ARCHETYPE: MM
POWER NAME: Thugs
PET NAME: Gabe, Samuel, Firestarter, Pain, Pleasure and Bruiser
SCREENSHOT(S): Fully upgraded thugs
ARCHETYPE: MM
POWER NAME: Necro
SCREENSHOT(S):
Zombies, middle w/1st upgrade
Grave Knights, left one with 1st upgrade
Lich w/1st upgrade
When doing some screenshots for art I'm planning on completing someday (really, I am) I took some screenies some some fire pets of someones. No idea whose they are, but they can be found here.
"If I fail, they write me off as another statistic. If I succeed, they pay me a million bucks to fly out to Hollywood and fart." --- George A. Romero
"If I had any dignity, that would have been humiliating" --- Adam Savage
Virtue Server: Kheprera, Malefic Elf, Lady Omen, Night Rune, La Muerte Roja, Scarab Lafayette, Serena Ravensong, Kyrse, and Arachnavoodoo among others.
These are all great! Keep them coming!
I hadn't seen the Fly Trap before, George looks really neat!!
Yes, screenshots may be more boring than fan art, but this one's for a good cause!
I have not been able to find ANY website that has pictures of allll the various pets that players can acquire in CoX. With that being said, I challenge these boards to come up with as many pictures of pets as possible! Everybody who has a character that can summon anything should be snappin' some screenshots! Controllers, Masterminds, heck, even Defenders and some other villains. Got a temporary power that gives you a pet? Screenshot that too!
Let's get a good database going of what everything looks like. Personally, I've never even seen Jack Frost or an Animated Stone. And fuhgeddabout any of the higher-level Mastermind pets; I've never gotten that high (I think I need the screenies as inspiration!)
So! In order to make this more database-y, let's follow a simple form:
ARCHETYPE:
POWER NAME:
PET NAME: (cookies for creativity!)
SCREENSHOT(S):
If you have multiple pets on one toon (Masterminds, Illusionists), just fill one out for each type of pet.
Let's see how this goes!!