Before someone says "its not even out yet" by me asking them one week before its added, we can probably add atleast a few more achievements as it shouldn't be too hard to implement. by now I believe that there is no sign that there is any new achievements for witches festival and only the same motifs, masks, and 2 "new" masks that are just reskins of the old masks, some new furnishings I think, but you can buy some already in the vendor in elden root...
Anyway no new achievements, 2 reskinned masks, and some furnishings you can already buy from the capital city vendor for a while (correct me if they are some from the plunder skulls as well) there isn't really new content for the people who were here last year. "but I need time I wont have time for all the achievements because I need to xp grind!" there is always other holidays in the year that have the xp buff, its not exclusive to witches festival. "BUT I HAVE MORE THAN ONE CHARACTER OP! How am I supposed to get all the achievements on all my characters" with limited time events you have next year but I do believe zos needs to make holiday event achievements accountwide. "but this event will be new for many players op" doesn't mean old players should be punished with the same repeat content. 2 reskinned masks and a xp buff many of us cant use isn't going to count as additional content
tldr add some replayability to the people who were here last year by adding achievements
Heres some idea
Loot 150 plunder skulls
place a witches festival item in your house
Defeat another player in a dual or in pvp while in skeleton polymorph
Complete a daily quest while polymorphed
Complete a dungeon while polymorphed
etc
and add an achievement for the orange dye