Pictures if you can show them pretty please! 
Mage Tower.
Vestments of the Purifier.
Cruel Gladiator’s Satin Armor - Legion Season 3/4
ToS Raid.
The tier 5 set is probably the best holy looking set.
My personal favorite is the mythic Antorus set.
Sorry, I can’t include links in my post yet
The new Aberrus Tier set, specifically the Normal difficulty color, is one of the best looking High Fantasy Priest sets in a long time. [The Furnace Seraph’s Verdict (Normal Recolor)]
For a less flashy, more conservative look, one of the Classic WoW priest looks has to be my favorite. [Royal Ascension Regalia (Black and White Recolor)]