I really like this event. So far I have no criticisms, and am enjoying myself very much. Kudos, and great job.
Felt the need to better explain why I like this event so much, because I would love to see events like this in the future:
1. The quest is doable by all classes, at all levels. Obviously better geared people have a better opportunity, but low levels are able to participate.
2. The quest is repeatable. Personally, I love repeatable quests like this. You know exactly what you need to do, and it's simple, but fun.
3. It's "timed." On a busy night, the snowman procs and melts on a fairly quick cycle, that you can rush to collect snowballs from. It's really fun because if you can't get all 200, you have to choose between a lesser chance, or skipping and getting the guarantee.
4. Monsters drop more than 1 of the item, and the collection isn't outrageous. It's nice to think you're actually making progress.
5. The prizes are nice. Headgears are always interesting, but there are some rare ones, like the snowman hat [1] that drops Buche De Noel, and the service ticket, that are worth a good chunk of Zeny, and make it worth it to stick it out even after getting a few headgears.
My only suggestions for future events like this:
1. Make all monsters in game (if possible and not too much work) drop a single snowball at a random chance (say, 10-25% chance). That way, people can sort of participate, while still doing other things.
2. slightly increase the chance for better prizes. Seems like that wouldn't be too difficult to do, and shouldn't be too OP, with the slow rate I've seen people in game actually get these items (could be based on my perception, which might just be unlucky in terms of how few people I've seen get snowman hats and service tickets.)