I'm in the final stages for the Ad Infinitum legendary backpack (https://wiki.guildwars2.com/wiki/Ad_Infinitum), and I wanted to drop a note about one of the components you craft as part of the collection, the Fractal Capacitor.
The reason I bring it up is while it's not even the precursor to the legendary back piece, it still has an awesome skin all on its own. In fact, some players might decide to start the collection just to get to this skin.
It has four stages:
1: https://wiki.guildwars2.com/wiki/Prototype_Fractal_Capacitor - purchased from fractal vendor
2: you then infuse it in the Mystic Forge
3: the infused capacitor is then used to craft https://wiki.guildwars2.com/wiki/File:Beta_Fractal_Capacitor_(Infused).jpg
4: You then turn the Beta Fractal Capacitor into its final form https://wiki.guildwars2.com/wiki/File:Fractal_Capacitor_(Infused).jpg
Thing is though, the screenshot on the wiki doesn't do the skin justice.
Here is a YouTube vid that shows all versions of this back piece: https://youtu.be/siZS0bgQpd8
Skip to 1:23 if you don't like waiting.
You can also use the wardrobe function of your Bank to preview it on your character.
I'm making the Ad Infinitum for my Guard, but I'm almost torn on the idea of just using this skin as its fits his armor and color palette perfectly, and even stays out of the way of the GS sheathed across his back. I don't see this skin on a lot of players, but it's sure worth considering.