I made a suggestion in another thread for potential Timewalking rewards.
Basically, one potential reward we could have for Timewalking is to have armor pieces or sets that are wither no longer in the game, haven't been completed because of a few missing pieces, or have never been released (at least to players).
This way, not only do you have the choice to either go for the mounts, but you could also go for armor and weapons for transmogging purposes (as a transmogger myself, I would be greatly in favor of this idea, but that's me).
One example for WotLK side of TW, you could have the blue warrior ICC tier set seen on Muradin, or have the missing pieces for the red varient:
For TBC, paladins and other plate-wearers could complete the white Crystalforged set look if they bring back missing pieces:
Also, we could reintroduce weapons and/or shields that sadly never did see the light of day:
What do you guys think? Should Timewalking also include ways to get armor and weapons that were either removed, or never put into the game?