The unique armour sets from the trading post have been great like the Darkmoon harlequin, harvester and love witch. That we could get sets like what Sylvanas and Varian wore is cool and I think that should be expanded upon to other characters. Examples:
• Lady Liadrin’s unique set from her artwork (also that shield/sword she has already in-game)
• Valeera’s iconic armour
• A re-design of the Sylvanas set but blue for those who prefer a more high elven look (and red/gold for blood elves)
• A dress based off Queen Azshara’s design in War of the Ancients
• Archmage Arugal’s helm/shoulders
• Lord Godfrey’s black coloration of the cata set (only red & white have been obtainable so far)
• A green variation of the Antoran Charhound mount, since they are demons there should be a fel coloration of them!