Duskhawk is in mostly Axeclaw, with the Golden Bow of Quel'Thalas, the requisite straw hat, and the awesome, awesome belt with 3D pouches (Girdle of the Legion General). I'm going to be mogging this bow forever.
Throop's got a much more eclectic mix; she's a prot warrior for the most part. The chest and pants are from the goblin quests in Spires of Arak; the boots are from Wrath blacksmithing; the shoulders (which move) were out of a missions chest. The shield is the Drillborer Disk from Molten Core, and the sword is an artifact of her Swordsmithing days, the Blazing Rapier. (Throop also makes appearances in Enchanted Thorium, since she can make it.)
Noski is in mostly Season 2 and Season 3 PVP gear, which tells you how long it's been since I did arenas regularly. The shoulders used to become transparent, taking your shoulders with them, when you'd stealth. (They've fixed that.)
Elsabeth's transmog is one of my favorites; the Mistscape Robe was a random drop while leveling an alt, and it just went so well with the Rime-Rift Shoulders and Derevka's Gleaming Girdle. The Communal Staff was in my bank for months before I finally got something to drop that I could mog it to; I had a 1-hand and offhand forever. Apparently the only 1-hand I have banked on her to use for transmog is the Mallet of Zul'Farrak.
Duskmoon is the other hunter with a transmog; my Nelf only has vanilla PVP gear banked for cohesive sets, and my third Horde hunter doesn't have anything cohesive complete (though I want the set from the Cataclysm endgame dungeons for her; she's got that bow). Anyway, Duskmoon's mostly in Wrathfin armor, with some random kind of matching shoulders (Calcified Web Spaulders) and Boots of Savagery. Normally I give her a crossbow, but she's got the Farstrider's Longbow at the moment.
The shaman's in the heirloom parts of the Elements, with a bit of I think tier 1 filling in some of the gaps. And then she's got Gorehowl, because I thought it was funny to do Elemental or Resto with Gorehowl and I can't mog her staff to Sulfuras. The Elements is the iconic shaman set for me.
Katrine's in pretty much full Tier 1, Felheart, because it looks awesome on a goblin. Yes, that scythe is Soul Harvester, and it killed my cropping options for the picture.
Dawning is in full Emerald Plate and I love her in it. The Knight's War Hammer was apparently stashed in her bank years ago, and the shield is the Emerald Shield. She totally looks like a tauren paladin working for the Cenarion Circle.
My death knight's in a similarly complete set - Warleader, with the Darkened Broadsword. The green matched her a little better before the model revamp.
Zaala's set (she was named before I ran into Zaela, all right?) was a bit harder to come by - the robes were a random drop, but matched the mage trainers in Orgrimmar (this was before the Siege raid, ahem), but filling out the rest of the pieces has been a pain. So with the Windchaser Robes I've got Mooncloth Shoulders, Icemist Bracelets, Regal Gloves, and the Lunar Belt. This set was complicated partly because this shade of the robes doesn't have most of the matching pieces implemented for players; there's three same-model/differently-shaded versions of it with more pieces, but this was the one that matched the trainers. I spent more than I should have on the belt. Ahem.
Evenmoon was made as a placeholder before my server got connected, to see what our soon-to-be neighbors' auction house was like. Since I didn't have a monk, I kept her to level once she was in the guild... and then boosted her, which left me really lost for a while. But I got a full set of Wolf Rider gear for her! I don't have the shoulders I really want for this (Rageclaw Shoulder Pads) because they've been super expensive every time I've seen them, but the Emblazoned Shoulders substitute okay. The staff is one of the low-level monk quest ones, since it matches well enough.
I still need transmog sets for my druid and two hunters, but I'm still drake farming, so that's been taking priority.