This information comes from the following thread on WoWhead: 5.2 PTR: New Troll Transmog Gear - Wowhead News
So, in 5.2, many of the old Troll designs / colorizations are coming back, as ilvl 429 BoE greens. The source of these items are unconfirmed, but will most likely drop from the Zandalari world spawns. These could potentially sell for quite a bit, so be on the lookout for them when 5.2.0 drops. Anyways, on to the real stuff.
Zul'Aman
Cloth
Many players liked the Robes of Heavenly Purpose from level 70 Zul'Aman, which was removed in 4.1. It was replaced with a green and brown version in Cataclysm, which also had matching accessories to form Amani Regalia.
It appears the blue version is back, along with more matching armor:
Forlorn Loa-Binder Cage - Item - World of Warcraft
Forlorn Loa-Binder Robe - Item - World of Warcraft
Forlorn Loa-Binder Shoulders - Item - World of Warcraft
Forlorn Loa-Binder Belt [do not use] - Item - World of Warcraft
Leather
The original level 70 Zul'Aman had a black leather set with items such as Shadowtooth Trollskin Cuirass, which was removed in 4.1. This was replaced by green and red Cataclysm variations on this black leather set.
The Timeworn Shadowtooth pieces are recolors of this original black set.
Timeworn Shadowtooth Belt - Item - World of Warcraft
Timeworn Shadowtooth Boots - Item - World of Warcraft
Timeworn Shadowtooth Cuirass - Item - World of Warcraft
Timeworn Shadowtooth Grips - Item - World of Warcraft
Timeworn Shadowtooth Shoulderpads - Item - World of Warcraft
Timeworn Shadowtooth Trousers - Item - World of Warcraft
Timeworn Shadowtooth Wristwraps - Item - World of Warcraft
The Amani Chain set dates from level 70 Zul'Aman--unlike other armor sets from this period, this set is mostly still obtainable as many items had identical skins to Justice Point gear. A purple version was added in 4.1: Amani Mail.
The Brittle Flamereaver pieces provide alternate ways to get the original red version.
Brittle Flamereaver Belt - Item - World of Warcraft
Brittle Flamereaver Bracers - Item - World of Warcraft
Brittle Flamereaver Gloves - Item - World of Warcraft
Brittle Flamereaver Hauberk - Item - World of Warcraft
Brittle Flamereaver Leggings - Item - World of Warcraft
Brittle Flamereaver Mask - Item - World of Warcraft
Brittle Flamereaver Pauldrons - Item - World of Warcraft
Brittle Flamereaver Treads - Item - World of Warcraft
Plate
The Tarnished Fanatic items resemble plate gear from the original ZA. This armor design comes in three colors, two of which are nearly identical: blue, red, and red/purple.
The new items are in the red/purple variation.
Tarnished Fanatic's Battlevest - Item - World of Warcraft
Tarnished Fanatic's Deathgrips - Item - World of Warcraft
Tarnished Fanatic's Girdle - Item - World of Warcraft
Tarnished Fanatic's Headcover - Item - World of Warcraft
Tarnished Fanatic's Pauldrons - Item - World of Warcraft
Tarnished Fanatic's Shackles - Item - World of Warcraft
Tarnished Fanatic's Warboots - Item - World of Warcraft
Tarnished Fanatic's Wargreaves - Item - World of Warcraft
Weapons
Gun: Hexbelcher Rifle - Item - World of Warcraft
Staff: Thunder Eagle Staff - Item - World of Warcraft
Dagger: Discarded Strikeblade - Item - World of Warcraft
Fist Weapon: Dull Hawktalons - Item - World of Warcraft
Staff: Sky-Shaper Staff - Item - World of Warcraft
One-handed Sword: Saur-Singer Spellblade - Item - World of Warcraft
Bow: Restrung Voodoo Bow - Item - World of Warcraft
Zul'Gurub
Cloth
The Exiled Dabbler gear resembles Demoniac's Threads, the old ZG Warlock set. These models were reused for several popular vanilla items, Royal Ascension Regalia.
Exiled Dabbler's Bracer - Item - World of Warcraft
Exiled Dabbler's Cinch - Item - World of Warcraft
Exiled Dabbler's Gloves - Item - World of Warcraft
Exiled Dabbler's Leggings - Item - World of Warcraft
Exiled Dabbler's Mantle - Item - World of Warcraft
Exiled Dabbler's Robe - Item - World of Warcraft
Plate
The Primordal Bloodsoaked items resemble Vindicator's Battlegear, the removed ZG warrior set. This was a popular plate model in vanilla, used for the Scholomance Deathbone set as well as many other plate items.
Primoridal Bloodsoaked Belt - Item - World of Warcraft
Primoridal Bloodsoaked Gauntlets - Item - World of Warcraft
Primoridal Bloodsoaked Greaves - Item - World of Warcraft
Primoridal Bloodsoaked Legplates - Item - World of Warcraft
Primoridal Bloodsoaked Pauldrons - Item - World of Warcraft
Primoridal Bloodsoaked Vambraces - Item - World of Warcraft
Primordial Bloodsoaked Breastplate - Item - World of Warcraft
The Forgotten Peacekeeper items resemble Freethinker's Armor, the removed ZG paladin set. It is a gold recolor of Dark Iron Plate, a black and red transmog set consisting of crafted fire resistance gear.
Forgotten Peacekeeper Boots - Item - World of Warcraft
Forgotten Peacekeeper Gauntlets - Item - World of Warcraft
Forgotten Peacekeeper Gauntlets - Item - World of Warcraft
Forgotten Peacekeeper Leggings - Item - World of Warcraft
Forgotten Peacekeeper's Armguards - Item - World of Warcraft
Forgotten Peacekeeper's Belt - Item - World of Warcraft
Forgotten Peacekeeper's Breastplate - Item - World of Warcraft
Forgotten Peacekeeper's Shoulders - Item - World of Warcraft
Weapons
One-handed Axe: Zandalari Head-Cleaver - Item - World of Warcraft
Gun: Gurubashi Dwarf Destroyer - Item - World of Warcraft
Wand: Rustic Voodoo Wand - Item - World of Warcraft
Two-handed Polearm: Ritual Headcleaver Halberd - Item - World of Warcraft
One-handed Axe: Corroded Hacker - Item - World of Warcraft
Two-Handed Axe: Weighty Stone Axe - Item - World of Warcraft
Dagger: Chiseled Fangs - Item - World of Warcraft