Below is a list of all pieces of Item Level 264 Plate for a Holy Paladin (not including ICC10H), by slot - with location and itemization (followed by Trinkets, Librams, and so forth). Please note that, unless otherwise noted, bosses listed are located in ICC25 (because this is what we're raiding as a guild, currently).
In almost all cases, for a Holy Light focus Paladin, crit/haste and haste/mp5 pieces are Best in Slot. In regards to T10, the Helm and Shoulders are the two best pieces to get (the four-piece bonus is lackluster).
Flash of Light focus Paladins should be concerned primarily with stacking Spell Power, and so have more flexibility in what pieces they pick up (go for lots of Spell Power).
I made this list mostly out of boredom:
Head:
Faceplate of the Forgotten - Festergut, crit/mp5
Sanctified Lightsworn Headpiece – T10, 95 Frost Badges + Armor Token, crit/haste
Neck:
Holiday's Grace – Festergut, crit/mp5
Blood Queen's Crimson Choker – Blood-Quen Lanathel, crit/haste
Shoulders:
Rusted Bonespike Pauldrons – Lord Marrowgar, crit/mp5
Sanctified Lightsworn Spaulders – T10, 60 Frost Badges + Armor Token, crit/haste
Chest:
Chestplate of Unspoken Truths – Vendor, 95 Frost Badges, crit/mp5
Rot-Resistant Breastplate – Rotface, crit/haste
Sanctified Lightsworn Tunic – T10, 95 Frost Badges + Armor Token, crit/haste
Belt:
Belt of the Lonely Noble – Random ICC drop, crit/haste
Lich Killer's Lanyard – Vendor, 60 Frost Badges, crit/haste
Waistband of Righteous Fury – Gunship, crit/mp5
Legs:
Leggings of Dying Candles – Valithria Dreamwalker, crit/mp5
Puresteel Legplates – Blacksmithing (8 Primordial Saronite), crit/haste
Sanctified Lightsworn Greaves – T10, 95 Frost Badges + Armor Token, crit/mp5
Feet:
Boots of the Funeral March – Valithria Dreamwalker, crit/mp5
Protectors of Life – Blacksmithing (5 Primordial Saronite), crit/haste
Wrists:
Crypt Keeper's Bracers – Prince Valanar, crit/mp5
Hands:
Fallen Lord's Handguards – Lady Deathwhisper, crit/haste
Gauntlets of Overexposure – 60 Frost Badges, crit/haste
Sanctified Lightsworn Gloves – T10, 60 Frost Badges + Armor Token, crit/mp5
Fingers:
Incarnadine Band of Mending – Blood Princes, crit/mp5
Marrowgar's Frigid Eye – Lord Marrowgar, haste/mp5
Ring of Rapid Ascent – Gunship, crit/haste
Trinkets:
Tears of the Vanquished – The Black Knight (ToC5), 84 Int, +500 mana on proc
Darkmoon Card: Greatness – Inscription, 90 Int, +300 Int for 15 sec on proc
Pandora's Plea – Mimiron (Ulduar25), 108 Int, 751 spell power for 15 sec on proc
Sliver of Pure Ice – Lord Marrowgar (ICC10), 158 spell power, +1625 mana on use every 2 min
Purified Lunar Dust – 60 Frost Badges, 179 spell power, +304 mp5 for 15 sec on proc
Talisman of Resurgence – 50 Triumph Badges, 128 Int, +599 spell power for 20 sec on use every 2 min
Solace of the Fallen – Lord Jaraxxus (ToC25), 150 spell power, +16 mp5 for 10 sec, stacks 8 times
Meteorite Crystal - +60 mp5, stacks with each spell cast within 20 sec, for 20 sec
Back:
Drape of the Violet Tower – 50 Frost Badges, crit/mp5
Frostbinder's Shredded Cape – Valithria Dreamwalker, crit/haste
Weapon:
Trauma – Rotface, proc (AoE HOT)
Bloodsurge, Kel'Thuzad's Blade of Agony – The Lich King, crit/haste
Royal Scepter of Terenas II – The Lich King, crit/haste
Rigormortis – Professor Putricide, haste/hit (eww hit… upgrade take if all the sword users have it)
Off-hand (shield):
Bulwark of Smouldering Steel – Lord Marrowgar, crit/haste
Libram:
Libram of Renewal – 15 Heroism Badges, reduces mana cost of Holy Light by 113 (the best libram for Holy Light focus)
Libram of Veracity – 25 Triumph Badges, Holy Light gives +234 spell power for 15 sec
Libram of Blinding Light – 30 Frost Badges, Holy Shock gives +85 spell power for 15 sec, stacks three times
Wrathful Gladiator's Libram of Justice – 1260 Arena Points and 1700 Arena Rating, increases spell power of Flash of Light by 510 (great for Flast of Light focus)
