The developers of at Blizzard implemented ideas that had been swirling around the community for the last few years. I had my own concept for a wardrobe called "Vaporization". The Illidan Decoy and Victor Alonso came up with a wardrobe concept that also included monetized seasonal sets. Many people had asked for it, and Blizzard made good on delivering it!
If you are here, you've probably started a hefty collection of your own. The account wide feature, simply put, is amazing. All items that you have saved in your character banks and void storage are automatically added to your collection, allowing you to vendor many items taking up space, and keeps them in your collection. It works across your entire battle.net account, so you can collect on any character, server, and across multiple Warcraft accounts. In my case, I have an Alliance account and a Horde account. (It harks back to the days of faction separation within a server, in case you were curious.)
When you first opened your wardrobes, you might have noticed that there are a lot of items you've don't remember having collected. The Warcraft developers went through considerable effort, finding all the quests you've completed throughout your career, and put all the rewards that you could have chosen from into your wardrobe. It caught quest items I had long since handed to a vendor. Pretty handy, considering many quests have changed. Many unique items, especially at lower levels, are preserved in your wardrobe!
I'm probably telling you lots you already lots that you know. Still, there are many things to do in Legion. Even if you aren't into the content, the transmogrification options opening up for every expansion will keep you busy for ages. Have fun collecting, designing, and of course transmogrifying all your sets!
If you have been following me @mogsaddiction page on Twitter, glad to have you stopping by my site. If you haven't seen my page, I do weekly Warcraft giveaways, and always like seeing what you have to share. Stop on by and give me a follow, if you dare! Until next time, remember the always important phrase: MOG ALL THE THINGS! :p