You read it. Costumes to go with the masks. I'll cover something else I saw with more detail too.
First of all, the costumes! These would probably be reskins of existing armors and costumes with some new features. There isn't much to say about these, other than the appearance and the styles. Costumes would come in three styles: Cheep, Replica and Authentic.
(Future Horseclaw to add images)
The Spookat Costumes would first look like a pink version of the Black Kat Cloak, then the Pink Angel armor (This but pink) and finally end at a Pink Cat Suit. All styles have a built in Pink Cat Tail.
Next would be the Frankenzom Armor Costume. The cheap version would look like a Fencing Jacket with some prismatic streaks, and two prismatic Dust Zombie fingers at the hands. The next version would look like the Cobalt Armor with the same streaks and fingers. And the Authentic version would have the same prismatic features of the previous two styles, but would look like a Dread Skelly suit. Also, all the costumes would be mostly grey.
The Phantom Armor would look like a Cloak. Starting off with a reskin of the Black Cat Cloak again, and ending with Azure Guardian Armor with a black scarf and a black cape.
And finally, the Scarab armor would always have "Scarab Wings". These are basically the wings of a Grave Scarab put on to the back of a knight. They occasionally flutter. This style would start as looking similar to a Fencing Jacket again, but would end up looking somewhat like Plate Armor.
Now for another feature. There are some people who like the Paper, Cheap (See above), and Replica styles of the Halloween costumes. I would suggest that an Authentic Mask/Costume could be crafted at a Mysterious Alchemy Machine for 1 Punkin Sprout for the Paper/Cheap style, and 3 for the Replica Style. This would turn them into Authentic Paper/Cheap/Replica Phantom/Frankenzom/Scarab/Spookat Mask/Costume. E.g Authentic Replica Scarab Mask.
Now that I've said all this, I'd like some feedback on these ideas. You can't really go wrong with costumes, anyhow.
Costume armors to match the masks? Agree totally. Lots of people love the scarab mask, but don't like not having much to match it with. Love the idea of having scarab wings. But I don't like the idea of having craftable costumes, it just sorta feels weird to me. I'd like for the frankenzom suit replace my body with a frankenzom monster body (like the gremlin suit) but hey, skelly is definitely in the mood of the spooky season. I'd like to look a lot more like the phantom in graveyards, and why not have a big fuzzy pink aura built-in? Finally, seraph wings on that lovely spookat body, minus the pink cat tail, since spookats don't have cat tails, and more of a fancy style to match the existing Spookat masks. This is just to keep the "monster mimic" feel of the candy costumes.
Your costume designs are awesome and I love them, and I'd love for them to be color/form variants of the main candy costumes, perhaps tied in to different lore. OOO loves them color variants. Or! I think your costumes could be reskins of actual armors (valkyrie, dread skelly, and Fallen), and be obtained via a sort of Dark Harvest event-exclusive "danger prestige" - like the winterfest reskins in "Grinchlin Assault!"