Contender Outfits: You are absolutely allowed to wear the contender outfits, despite them being blue-quality because they are considered toys, however, if you engage in Contender Battles and die… that does count as a death for your Challenger.
Honor the Dead buff: This buff is achieved by doing a /dance with either Catrina or Chapman. It is allowed because the buff is only cosmetic and does not give you any boosts.
Bread of the Dead: This food is allowed to be eaten, however, be aware that it does give a Well Fed buff (+all-stats for an hour), so you must right-click that off once you get it.
Candy Skull: This food is allowed.
Spirit Candle: This provides a spirit buff, so it’s not allowed.
Whimsical Skull Mask: This is a cosmetic item and since it’s only white-quality, you are allowed to wear it.
Macabre Marionette: You are absolutely allowed to quest to obtain the pet for your own personal collection, however, it does not give you a free pass to start leveling by pet battles. You are still held to the 9 pet battle limit.