Hongdae Daiso: No.2 (양화로 182) and Hongik Univ.

(홍익로 25), both 10:00–22:00. Photo day? 「스티커 얼굴 꾸미기」 face deco stickers are ₩3,000 (261 reviews, 4.8). Stickers aren't liquids, so no carry-on worries.