We've had quite a few new headwear options added to the game's costume selection lately, but what we don't have (yet) are helmet options. A lot of NPCs in the world seem to mix and match the helmet of one costume with the body of a different costume, and that adds a level of variety that players can't replicate.
Having the option to wear the Lion Guard Knight helmet with the Covenant Scout armour, mixing Nedic armour with a Nord helmet, or an Imperial helmet with Shrouded Armor, a faction-appropriate helmet with your Alliance Rider Outfit... there's a lot of potential variety there, all using the helmet part of costumes / armour styles that already exist (which should make it relatively easy to implement?)